Ingredients

• 2 3/4 cups all-purpose flour
• 2 tablespoons granulated sugar
• 1 3/4 teaspoons kosher salt
• 1 1/4 cups (2 1/2 sticks) chilled unsalted butter, cut into pieces
• 3/4 cup raw skin-on hazelnuts
• 1/3 cup plus 1/4 cup granulated sugar
• 4 tablespoons (1/2 stick) unsalted butter, room temperature
• 2 tablespoons buckwheat flour
• 1/2 teaspoon rye whiskey or vanilla extract
• 1/4 teaspoon kosher salt
• 2 large eggs
• 1 1/2 pound rhubarb, halved lengthwise, cut into 2 1/2" pieces
• 1 tablespoon finely grated orange zest
• 3 tablespoons fresh orange juice
• All-purpose flour (for surface)
• 1/2 cup demerara sugar
• 1 tablespoon aniseed

Instructions

1. Pulse flour, granulated sugar, and salt in a food processor to combine. Add butter and process until mixture resembles coarse meal with a few pea-size pieces of butter remaining.
2. Transfer mixture to a large bowl; drizzle 1/3 cup ice water over. Gently mix with your hands until a shaggy dough forms.
3. Turn out dough onto a lightly floured surface and knead once or twice, pressing to incorporate any dry bits of flour. Divide dough into 2 pieces and flatten each into about a 1"-thick disk. Wrap in plastic wrap; chill at least 1 hour.
4. Do ahead Dough can be made 2 days ahead. Keep chilled, or freeze 1 month.
5. Dough can be made 2 days ahead. Keep chilled, or freeze 1 month.
6. Filling and assembly: Preheat oven to 350°F. Process hazelnuts and 1/3 cup granulated sugar in a food processor to a fine paste, about 3 minutes. Add butter, buckwheat flour, rye, salt, and 1 egg and pulse until smooth; set frangipane aside. Toss rhubarb, orange zest and juice, and remaining 1/4 cup granulated sugar in a medium bowl. Let sit, tossing occasionally, 10 minutes. Whisk remaining egg in a bowl with 1 teaspoon water. Divide each disk of dough into 4 pieces. Roll out a piece of dough on a lightly floured surface to make a 5" round. Spread with about 1 1/2 tablespoons reserved frangipane, leaving a 1" border. Brush border with egg wash. Top frangipane with some rhubarb; fold edges of dough up and over rhubarb, overlapping slightly. Brush dough with egg wash. Repeat process to make 7 more galettes. Transfer to parchment-lined baking sheets. Sprinkle galettes with demerara sugar and aniseed and bake, rotating once, until crust is golden brown and rhubarb is soft, 30–40 minutes. Let cool on a wire rack. Do ahead: Galettes can be baked 3 days ahead; store tightly wrapped at room temperature.
7. Preheat oven to 350°F. Process hazelnuts and 1/3 cup granulated sugar in a food processor to a fine paste, about 3 minutes. Add butter, buckwheat flour, rye, salt, and 1 egg and pulse until smooth; set frangipane aside.
8. Toss rhubarb, orange zest and juice, and remaining 1/4 cup granulated sugar in a medium bowl. Let sit, tossing occasionally, 10 minutes.
9. Whisk remaining egg in a bowl with 1 teaspoon water. Divide each disk of dough into 4 pieces. Roll out a piece of dough on a lightly floured surface to make a 5" round. Spread with about 1 1/2 tablespoons reserved frangipane, leaving a 1" border. Brush border with egg wash. Top frangipane with some rhubarb; fold edges of dough up and over rhubarb, overlapping slightly. Brush dough with egg wash. Repeat process to make 7 more galettes. Transfer to parchment-lined baking sheets.
10. Sprinkle galettes with demerara sugar and aniseed and bake, rotating once, until crust is golden brown and rhubarb is soft, 30–40 minutes. Let cool on a wire rack. Do ahead: Galettes can be baked 3 days ahead; store tightly wrapped at room temperature.