4 c flour ( plus some for the board)
2 t baking powder
2 t salt
6 oz Parmigiano-Reggiano, finely grated (1/4 c reserved)
3/4 c cold unsalted butter, cubed
4 large eggs
1 c whole milk
Put oven racks in upper and lower thirds of oven and preheat oven to 350°F.
Stir flour, baking powder, salt, cheese, and pepper in a large bowl. Cut in butter until mixture resembles coarse meal. Beat 3 eggs with milk, stir into flour mixture, stirring until a soft dough forms.
Turn dough out onto a lightly floured bread board and divide dough into 4 pieces. Flour hands and form each piece into a slightly flattened 12-inch-long log about 3/4 inch high. Transfer logs to 2 ungreased large baking sheets.
Beat remaining egg and brush some over logs, then sprinkle tops of logs evenly with remaining 1/4 cup cheese. Bake, rotating sheets 180 degrees and switching position of sheets halfway through baking, until logs are pale golden and firm, about 30 minutes total. Cool logs to warm on sheets on a rack, about 10 minutes.
Reduce oven temperature to 300°F.
Transfer 1 warm log to a cutting board and cut diagonally into 1/2-inch-thick slices with a serrated knife. Arrange slices, cut sides down, in 1 layer on a baking sheet. Repeat with remaining logs, transferring slices to sheets. Bake, turning over once, until golden and crisp, 35 to 45 minutes total. Cool biscotti on baking sheets on racks, about 15 minutes.
Yum. Great with a white bean purée.