This recipe can be used to make mini-muffins or mini-loaves. Into a bowl sift together the flour, the baking powder, the baking soda, and the salt. In a large bowl with an electric mixer cream together the butter, the peanut butter, and the brown sugar and beat in the eggs, 1 at a time. Beat in the buttermilk and beat the mixture until it is combined well. Add the flour mixture, beat the batter until it is just combined, and stir in the chocolate chips. Divide the batter among 5 buttered and floured loaf pans, each 5 3/4 by 3 1/4 by 2 inches, and bake the breads in the middle of a preheated 350 oven for 40 to 45 minutes, or until a tester comes out clean. Remove the breads from the pans and let them cool, right sides up, on a rack. The breads keep, wrapped well in plastic wrap and foil, chilled for 1 week or frozen for 1 month. Makes 5 small loaves.