1/4 cup unbleached all purpose flour
1/4 cup cake flour
pinch of kosher salt
2 large egg yolks
1 large egg
1/4 cup granulated sugar
1 1/2 tsp vanilla extract
4 tbsp unsalted butter, melted
1. Adjust oven rack to low center position; heat oven to 375 degrees. Sift flours and salt together in small bowl; set aside. Coat molds by mixing two teaspoons of melted butter with one teaspoon of all purpose flour. Brush the molds and rims thoroughly, but not thickly, with this mixture.
2. Beat yolks with whole egg in bowl of electric mixer until light yellow and fluffy, about 5 minutes on high speed if using hand mixer, about 3 minutes if using heavy-duty mixer. Add sugar and vanilla and beat until a ribbon drops from beaters, about 5 minutes with hand mixer, 3 minutes with heavy-duty mixer. Gently fold in flour mixture, then melted butter.
3. Spoon batter into molds. (Batter should come just flush with mold rim.) Bake until tops are golden and cakes spring back when pressed lightly, about 10 minutes. Turn madeleines onto dry tea towel; cool to room temperature. (Can be stored in airtight container up to 3 days or frozen up to 1 month.)