6medium pluots or plums, ripe but firm, (1 pound / 450 grams)
1-2tablespoonscoarse turbinado or granulated sugar, for sprinkling
Position a rack in the center of the oven and preheat to 350ºLine a standard muffin pan with paper liners (alternatively, grease the pans with softened butter and dust with oat flour, tapping out the extra.)
Melt the butter with the vanilla pod and scrapings in a medium saucepan over a medium flame. Continue cooking until the butter turns golden and smells nutty, 5-10 minutes, swirling occasionally.
Meanwhile, place the poppy seeds in a heatproof measuring cup. When the butter has browned, pour it into the cup with the poppy seeds. This will stop the cooking and enhance the flavor of the seeds. Set aside to cool at least 15 minutes. Remove the vanilla pod (you can rinse it, let it dry, and use it to make vanilla extract).
Meanwhile, in the bowl of a food processor combine the almonds, oat flour, rice flour, powdered sugar, muscobado sugar, and salt. Process until the almonds are finely ground. Blend in the egg whites until combined. With the motor running, pour in the cooled brown butter, leaving the poppy seeds in the bottom. (This helps the butter emulsify into the batter.) Turn off the motor, and stir in the poppy seeds and any remaining butter with a flexible spatula. (It helps to remove the blade.) The batter will be quite fluid. Divide the batter among the lined muffin cups; it will come about halfway up the sides.
Halve the plums and remove the pits. Place a half cut-side down, and cut with a sharp, serrated knife into 1/4" thick slices, discarding the two end pieces. Repeat with the other plums. Fan four or so slices atop each financier, and sprinkle the tops with coarse sugar.
Bake the financiers until they are puffed, golden on top, and a toothpick inserted into the center comes out clean, 25-35 minutes. Remove from the oven and let cool until warm; the cakes are still cooking from residual heat.
Serve the financiers warm or at room temperature.
Adapted generously from The Sweet Life: Desserts from Chanterelle.These little buttery cakes could really be topped with any fruit: berries, figs, nectarines, apricots, plums, peaches, cherries, pears, or poached quince, to name a bunch. Smallish pluots, sliced thinly, fit perfectly atop muffin-sized cakes, and they bake into jammy, glazed slices, their tartness offsetting the sweet cakes.Steeping poppy seeds in the warm butter helps to draw out their mysterious, nutty flavor. They give the finished cakes a crunch that I find completely addictive.If you prefer, you can make this with almond flour in place of the sliced almonds (use the weight measurement for accuracy) and mix the batter by hand in a large bowl. If gluten isn't an issue, you can replace the flours with 1/2 cup all-purpose or whole wheat flour, taking care to agitate the batter minimally so as not to develop the glutens.If gluten is an issue, be sure to use certified gluten-free ingredients (particularly oat flour and sugars).This batter uses 5 large egg whites. Whites keep for up to a week or two in the refrigerator, or they can be frozen for several months. If you're starting with whole eggs, use the yolks in an ice cream or custard such as crème caramel or crème brulée.The financier batter can keep airtight and refrigerated for several days if you don't wish to bake them all at once. The finished cakes are best the day of baking, but will keep for a day or two at room temperature, or longer refrigerated. Brush the plums with a bit of warm honey or plum jam if you wish to restore their sheen.All ounce measurements are by weight.Nutritional values are based on one of twelve cakes.