- 10 tablespoons unsalted butter, plus more, room temperature, for pans
- 1 1/4 cups skin-on hazelnuts, divided
- 1/2 cup all-purpose flour
- 1/2 teaspoons kosher salt
- 1 vanilla bean, split lengthwise
- 2 tablespoons honey, preferably raw
- 3 large egg whites
- 3/4 cup (packed) dark brown sugar
- Preheat oven to 350°. Butter eight 3×2″ mini loaf pans or a standard 12-cup muffin pan. Toast 1 cup hazelnuts on a small rimmed baking sheet, tossing occasionally, until golden brown, 8–10 minutes. Let cool (do not remove skins). Pulse hazelnuts, flour, and salt in a food processor until finely ground.
- Place 10 tablespoons butter in a small saucepan. Scrape in seeds from vanilla bean; add pod. Cook over medium heat, stirring often, until butter foams, then browns (do not let burn), 5–8 minutes. Discard pod and scrape vanilla butter into a medium bowl. Whisk in honey.
- Increase oven heat to 400°. Whisk egg whites in a large bowl just to break up, add brown sugar, and whisk until mixture is smooth. Fold in dry ingredients in 2 additions, then fold in butter mixture just until smooth.
- Coarsely chop remaining 1/4 cup hazelnuts. Scrape batter into pans and top with hazelnuts. Bake financiers until golden brown and a tester inserted into the center comes out clean, 15–20 minutes for loaves, 10–15 for muffins. Let cool 5 minutes in pans, then transfer to a wire rack. Let cool completely.
- DO AHEAD: Financiers can be made 1 day ahead. Store tightly wrapped at room temperature.