4 cups plus 1 tablespoon all-purpose flour, divided2 tablespoons baking powder 2 teaspoons salt 3/4 pound cold unsalted butter, diced 4 extra-large eggs, beaten lightly 1 cup cold heavy cream 1/2 pound extra-sharp yellow Cheddar, small-diced 1 cup minced fresh dill 1 egg beaten with 1 tablespoon water or milk, for egg wash
Preheat the oven to 400 degrees F.
Combine 4 cups of flour, the baking powder, and salt in the bowl of an electric mixer fitted with a paddle attachment. Add the butter and mix on low speed until the butter is in pea-sized pieces. Mix the eggs and heavy cream and quickly add them to the flour-and-butter mixture. Combine until just blended. Toss together the Cheddar, dill, and 1 tablespoon of flour and add them to the dough. Mix until they are almost incorporated.
Dump the dough onto a well-floured surface and knead it for 1 minute, until the Cheddar and dill are well distributed. Roll the dough 3/4-inch thick. Cut into 4-inch squares and then in half diagonally to make triangles. Brush the tops with egg wash. Bake on a baking sheet lined with parchment paper for 20 to 25 minutes, until the outside is crusty and the inside is fully baked.