Position a rack in the center of the oven, and preheat to 400 degrees.
In a medium bowl, sift together the cake flour, all-purpose flour, cream of
tartar, baking soda, and salt. Using a pastry blender or two knives, cut the
butter into the flour until the mixture resembles small peas. Add the half and
half, and stir gently just until a soft dough forms. Knead the dough in the bowl
a few times, just until smooth. Do not overwork the dough
