These crackers use mushroom powder made from dried mushrooms ground with a mortar and pestle or in a spice grinder; it adds a rich, earthy flavor to these savory snacks.
Preheat oven to 350 degrees. In the bowl of an electric mixer fitted with the paddle attachment, mix butter and goat cheese on medium until well combined. Add flour, mushroom powder, and pepper; mix until just combined and crumbly. Scrape down sides of the bowl, and add the milk. Mix on low speed until the dough comes together; it should be quite stiff.
Divide dough into thirds. Wrap two pieces in plastic wrap; set aside. On a lightly floured work surface, roll out third piece to 1/8 inch thick. Cut dough with a 2-inch cookie or biscuit cutter, arrange on a baking sheet, and prick each with a fork once or twice. Sprinkle with salt, and bake for 15 to 20 minutes or until the crackers start to brown.
Remove from oven; let cool on a wire rack. Repeat with remaining dough, rerolling scraps once. Serve when cool, or store in airtight container for up to 1 week.