Step 1

Preheat the oven to 350°F (176°C). Line 2 baking sheets with parchment paper.

Step 2

Combine the cheese, wheat or whole-grain spelt flour, all-purpose or white spelt flour, butter, milk, onion powder, if using, and salt in the bowl of a food processor fitted with the dough blade. Pulse to form a ball, 1 to 2 minutes. If the dough appears oily from the cheese, wrap it in plastic wrap and chill for 30 minutes.

Step 3

Turn the dough out onto a well-floured surface and roll it to 1/8 to 1/16-inch thickness. Lightly brush the dough with the milk. Using a pastry wheel or knife, cut the dough into 1-by-1-inch squares. Prick the center of each cracker with a skewer. Place the crackers on the prepared baking sheets, leaving at least a 1/2 inch between crackers.

Step 4

Bake the crackers, rotating the baking sheet halfway through baking, just until the crackers are slightly brown at the edges, about 10 minutes.

Step 5

The crackers will crisp up as they cool, so be careful not to overbake them, although if you like your crackers extra crunchy, leave them in the oven for 11 to 12 minutes. Transfer the crackers to a wire rack and cool completely.