Preheat oven to 350°F. Set butter out to soften.
Cut softened butter into pieces and add to a food processor with all remaining ingredients except for milk. Pulse the processor 5 seconds at a time 5 or 6 times until the dough is in coarse crumbs.
Add 1 tablespoon of milk and process until the dough gathers together in a ball. Add more milk little by little if needed.
Roll the dough out onto a floured surface until it is about 1/8 inch thick. (Make sure to flour your rolling pin as well.)
Cut the dough into 1-inch squares with a sharp knife or pizza cutter. (You can put a bit of flour on the blade of the knife as well to keep it from sticking.) Use the flat end of a wooden skewer to poke a hole in the center of each cracker.
Place the crackers at least ¼ inch apart on a parchment paper-lined baking sheet; bake for 12-15 minutes until the edges are just starting to brown.
Let the crackers cool completely before serving.