7 tablespoons butter (almost 1 stick), softened, plus more for greasing the pans
2 cups all-purpose flour, plus more for dusting the pans
3/4 cup sugar
2 eggs
1 teaspoon vanilla extract
1 teaspoon baking powder
1 cup blanched hazelnuts, toasted and chopped
Pinch salt
8 ounces dark chocolate, chopped
Instructions
Heat the oven to 375°F. Grease a baking sheet with some butter and dust it with flour; turn the sheet upside down over the sink and tap to remove the excess flour.
Use an electric mixer to cream together 4 tablespoons of the butter and the sugar until light and fluffy; add the eggs, one at a time, and beat until well blended, then add the vanilla. Combine the flour, baking powder, nuts, and salt in a medium bowl. Add the dry ingredients to the egg-butter mixture a little at a time, beating until just combined. Stop mixing when the dough holds little dimples after you poke and pinch it.
Divide the dough in half, roll each half into a loaf about 2 inches wide, and put on the prepared baking sheet. (Roll the loaves as uniformly as you can so the biscotti bake evenly.)
Bake for 25 to 30 minutes, rotating the position of the pan in the oven if necessary so they cook evenly, until they’re golden and beginning to crack on top. You want the dough to bake just enough to dry out and be slightly firm in the center. Cool the logs on the sheets for a few minutes, then transfer to a rack. Lower the oven temperature to 250°F.
When the loaves are cool enough to handle, carefully transfer them to a cutting board and use a serrated knife to slice each on the diagonal into 1/2-inch-thick slices. Put the cookies on the sheet, sliced side up; it’s okay if they are close to each other. Return the pan to the oven, and bake 15 to 20 minutes, turning the biscotti once, until they dry out. Cool them on racks.
While the biscotti are cooling, melt the chopped chocolate with 3 tablespoons butter in a small saucepan over low heat, stirring frequently. Put parchment paper or a baking sheet under the wire rack with the cookies to catch drips. Transfer the chocolate mixture to a cup or glass just big enough to hold it. When the biscotti are cool enough to handle, dip half of each cookie into the chocolate, tap against the rim to remove excess, then put them on the rack. As they continue to cool, the chocolate will harden a bit. (Store cookies between layers of parchment in an airtight container; they’ll keep for several days.)