12 tablespoons (1 1/2 sticks) unsalted butter, at room temperature
3/4 cup dark brown sugar
1/2 cup granulated sugar
1 large egg
2 teaspoons vanilla
1 cup (6 ounces) semisweet or bittersweet chocolate chunks or chips
1/2 cup chopped pecans
Place the rye flour, unbleached flour, baking powder, salt, and baking soda in a large bowl and whisk to combine. Set aside.
Place the butter and sugars in a large bowl, and beat with an electric mixer on low speed until creamy, 1 to 2 minutes. Add the egg and vanilla and beat until smooth. Add the flour mixture a little at a time, beating on low speed until all the flour has been added and the dough is smooth. Fold in the chocolate and pecans. Place the dough in the refrigerator at least 1 hour, preferably overnight.
When ready to bake, preheat the oven to 375 degrees. Scoop dough onto ungreased baking pans using a 1-inch scoop. Place one pan at a time in the oven and bake until golden brown but still a little soft in the center, 9 to 11 minutes. Repeat with the remaining dough. Let cookies cool on a rack until time to serve. These freeze well.