Preheat the oven to 350°F. Mix all the dry ingredients in a bowl. Melt the butter and then add the milk. Mix all of the ingredients together and let the dough rest for 10 minutes. Roll the dough very thin on parchment paper. Prick with a fork. Cut into square crackers about 2”x2”. Bake in the center of the oven for about 20 minutes. Let the crackers cool on the baking sheet. Break the crackers into pieces and store in an airtight container.