Financier is a sadly under appreciated pastry (along with the kouing amann, but that's another show), and its about time someone champions its richness, ease of preparation and above all, its use of brown butter. This miniature cake utilizes fresh, summer berries and highlights them in a moist, nutty medium. One can use feasibly any small fruit (and any nut flour/meal, for that matter), and it will work relatively seamlessly. Fruits with a high water content might add a few minutes to the final cooking time, though. I like the winey, tartness of blackberries in this application. Large berries, like strawberries, should be sliced into wedges before using in the recipe. If your berries are particularly juicy, it might help to freeze them before using, as they may smash during the process. —PieceOfLayerCake
raw pistachios, divided
unbleached, all-purpose flour
confectioners' sugar, plus more for dusting
fresh berries, of any variety (approx. 12 - 16 oz.)
Begin melting the butter in a small skillet, set over medium heat; have a small heatproof bowl standing by. When completely melted, turn the heat to medium-high and slowly begin to swirl the pan in a circular motion to distribute the heat evenly. The butter will foam intensely until all of the water evaporates out of the fat. When this happens the temperature will rise, and the milk solids in the butter will caramelize quickly. When the butter reaches a warm chestnut brown, immediately remove from the heat and dump the butter into the bowl. Stir it slowly with a heatproof spatula for a minute or so, to release some of the intense heat. Set aside to cool slightly, while you prepare the other ingredients.
In a food processor, place 100 g. of the raw pistachios and grind into a fine meal. Add the almond flour, confectioners' sugar, flour and salt. Pulse 5 - 10 times until well combined. Dump the ingredients into a large bowl and whisk to make sure everything is incorporated. Pour in the slightly cooled brown butter and work together with the whisk (or clean hands) until just incorporated.
Add in the egg whites and whisk until the batter is well combined and smooth. Cover the bowl with plastic wrap and allow to chill for at least 1 hour, or overnight.
When ready to bake, preheat your oven to 350℉. Generously coat 20 standard muffin cups with soft butter, then stash in the freezer, briefly to firm the butter. Pulse the remaining 50 g. of pistachios in your food processor until coarsely ground and divide evenly throughout the muffin cups. Place 2 - 3 of your berries in the center of each cup. Using a #16 portion scoop, or a 2 oz. measure, scoop 20 balls of chilled batter into each muffin cup, covering the berries. Take your fingers (I find it easier to wear a disposable glove) and smash each of the dough balls, allowing them to fill the cups completely.
Bake for 20 - 30 minutes, or until they're puffed, firm to the touch and slightly golden. Allow to cool in the cups for 5 minutes, and then turn out onto a wire rack before allowing to cool completely. Garnish with a light dusting of confectioners' sugar and serve.