I did not have any particular reason to make these tartlets other than the fact that this past weekend was a bank holiday weekend and after a few busy weeks at work and weekends away I suddenly found myself not only with 1kg of rhubarb that needed taking care of but also with ample time on my hands. Time clearly best spent making pate sucree, poaching rhubarb, stirring pastry cream and whipping meringue (the laundry always takes care of itself, doesn’t it?). Also, there is hardly anything better than starting your Sunday with a large cup of coffee and a pastry.
I don’t follow many rules when it comes to the recipes I share here. But one of my rules is that the recipes should have at least a hint of some inherent logic. So rhubarb is paired with buckwheat, as, botanically speaking, the two form part of the same family (together with sorrel and knotweed). In turn, buckwheat is paired either with flavours that are Northern French to me, like browned butter and salted caramel (as I can still vividly remember the buckwheat crepes from summer holidays in Brittany), or Japanese (thanks to my fondness for buckwheat soba and most things Japanese).
After spending most of my spare time in recent weeks reading about Japanese baking and intriguing bread recipes that rely on the likes of yeast water (made from fermenting fruit in water at room temperature), koji (the fungus responsible for creating sake) and miso as leavening agents/aids, Japanese flavours it was.
These little buckwheat tartlets are therefore filled with a thick pastry cream flavoured with shiro miso (the lightest and sweetest kind of miso), and topped with rhubarb that has been gently poached in sake, which gives the rhubarb this faint ‘winey’ note which I adore. The finishing touch was a few shards of toasted buckwheat studded meringue, which, while optional, provide a nice bit of crunch (and rather conveniently also takes care of the two egg whites left over from making the pastry cream). You could of course leave out the sake and the miso and use all spelt or all purpose flour for the pastry and you would still end up with delicious rhubarb custard tartlets, albeit more traditional in flavour.
Rhubarb Tartlets with Sake Poached Rhubarb, Miso Pastry Cream and Buckwheat Meringue
Note: While there are several components to this recipe, none of them are difficult per se and everything can be prepped in advance (safe for the glaze should you opt to make it). The one thing I should flag is that you should watch the rhubarb like a hawk while poaching it – rhubarb is so delicate it can go from tough to falling apart in an instant. While the latter won’t have any negative impact on the flavour of the rhubarb, it does make it somewhat more difficult to top your tartlets in any kind of orderly fashion. That being said, any soft and floppy bits of rhubarb together with their poaching liquid and the tiniest drop of rose water make a rather lovely topping for labneh, porridge or rice pudding. The tartlets are best served the day they are made but will keep for 1 day.
For the buckwheat meringue
2 egg whites
120g powdered sugar
2/3 tsp vinegar
50g toasted buckwheat groats
For the pate sucree
120g spelt flour
60g buckwheat flour
Pinch of salt
For the miso pastry cream (recipe loosely adapted from Ginette Mathiot’s The Art of French Baking)
250ml single cream
2 egg yolks
25g brown rice flour (alternatively you can use corn flour or tapioca starch)
2 tsp miso
For the poached rhubarb
750g rhubarb, trimmed and cut into 5cm long pieces
For the glaze (recipe adapted from Le Cordon Bleu London)
100ml poaching liquid from the rhubarb
2 gelatin sheets
To make the buckwheat meringue, pre-heat the oven to 100 degrees Celsius and prepare a sheet pan with parchment paper. Lightly oil the parchment paper with neutral-tasting oil like sunflower or peanut oil.
In a large mixing bowl whip the egg whites until the soft peak stage. Add the powdered sugar 1 tablespoon at a time, while whisking on high speed. Once all the sugar has been incorporated, add the vinegar. Continue to whisk for ca. 10 minutes or until the meringue is thick and glossy.
Fold in all but 1 tbsp of the toasted buckwheat groats. Spread the meringue thinly on the parchment paper, scatter the remaining buckwheat groats on top of the meringue and bake for 1-1.5h until firm and crisp. Leave to cool in the oven.
For the buckwheat pate sucree, start by creaming the butter with the sugar until light and fluffy – this will take ca. 5 minutes. Add the egg and beat to incorporate. Add the spelt flour and buckwheat flour as well as the pinch of salt and, using a spatula or large wooden spoon, stir the flour into the wet ingredients. At first the dough may seem far too dry and as though the wet ingredients will never absorb all the flour, but if you persevere, slowly but surely the flour will disappear and you will be left with a smooth and silky dough the consistency of play-doh. Wrap in clingfilm and place in the fridge to firm up for at least 1h.
Next, prepare the miso pastry cream. In a medium-sized sauce pan gently heat the cream until it starts to steam. While the cream is heating up, whisk the egg yolks, the egg, the sugar, the brown rice flour and the miso in a mixing bowl. Once the cream starts to steam take it off the heat and whisk about a third of the cream into your egg mixture, to temper the eggs. Pour the tempered egg mixture back into the sauce pan and return to the heat. Continue cooking the pastry cream on low to medium heat, whisking continuously, until it is very thick. This may take between 10 and 15 minutes but I prefer to do it this way than thickening the pastry cream more quickly over higher heat as I feel like I get more control over the cooking process this way and run less risk of cooking the eggs and curdling the pastry cream. Pass the pastry cream through a fine mesh sieve into a bowl and cover the bowl with clingfilm. Set aside to cool.
Pre-heat the oven to 200 degrees and prepare a sheet pan with parchment paper and six 10x2cm tartlet rings and have some baking beans and parchment paper ready. Lightly flour your kitchen counter. Gently knead the pate sucree until pliable (I like doing this by first tearing the pastry into walnut-sized pieces before kneading the pieces back together) and roll out very thin, ca. 3mm. Line the tartlet rings, cutting off any excess pastry with a sharp knife (you may have to reroll the pastry to do this).
Line each tartlet case with a piece of parchment paper (the easiest way to do this is to use squares of parchment paper slightly bigger than the tartlet rings, scrunching them up into a ball and then unfolding them – this helps to get the parchment paper flush against the pastry), and fill with baking beans. Bake for 12-15 minutes until the pastry is crisp and only just starting to colour. Set aside to cool.
Next, prepare the poached rhubarb. In a medium-sized saucepan bring the water, sugar and sake to a boil. In a large saucepan, arrange the rhubarb in a single layer (to ensure even cooking) and add the poaching liquid. Cook on medium heat for 7-10 minutes until al dente (keep on checking the rhubarb from the 6 minute mark and watch the rhubarb like a hawk – it really does go from firm but cooked to soft and mushy in an instant).
Prepare the glaze. In a bowl soak the gelatin sheets in cold water until soft – this will take ca. 10 minutes. While the gelatin sheets are soaking heat the poaching liquid in a small pot until it starts to steam. Squeeze the excess water from the gelatin sheets and add to the poaching liquid. Remove the pot from the heat and stir the poaching liquid until the gelatin is melted. Leave to cool to room temperature.
Spread a couple of tablespoons of the miso pastry cream on the bottom of each tartlet. Drain the rhubarb and lay a few pieces on top of the pastry cream, cutting the rhubarb into smaller pieces if necessary. Carefully spoon ca. 1tbsp of glaze over each tart. Leave to set (if your kitchen is not too hot, this should take no longer than 1 hour). Break the meringue into irregular pieces and place a few on each tartlet.
Any leftover poaching liquid makes a wonderful lemonade mixed with some sparkling water and some freshly squeezed lemon juice. I imagine it would also be rather lovely with some gin.