Combine dry ingredients, butter, and vanilla in a medium-sized bowl until crumbly. Add milk and mix. If using an electric mixer, watch very carefully for the crumbs to begin to clump slightly and form larger crumbs. As soon as they do, turn off the mixer. Do not over mix or the crumbles will turn into balls of dough. In the event of over clumping, break the dough into small pieces by hand.
Sprinkle over pies (or muffins!) One batch will cover 1 pie or 9 muffins.
When doubling this recipe, keep the measurements of wet ingredients the same to prevent over clumping.