Preheat the oven to 350 degrees F.

Add the walnuts, oats, salt, pepper, baking powder, and seasoning (if using) into a blender or food processor. Blend until they are the consistency of cornmeal. You may need to stop frequently to stir the ingredients if they begin to stick. Add the milk and blend until smooth. In 1 tablespoon increments, add additional milk as needed until it reaches the consistency in my photo.

Spread the batter onto a well-greased baking sheet or parchment-lined baking sheet with an offset or rubber spatula. Spread as thin and evenly as possible. Try to make sure the middle of the batter is not thicker than the sides. This will help the crackers cook evenly.

Bake slowly until delicately golden. After 10 minutes, remove from the oven and score into squares or rectangles using a pastry wheel or sharp knife. Return to the oven and continue baking until dry, about 20 to 25 minutes more. Thinner crackers at the edges will bake quicker than thicker ones. Watch your oven. If outside crackers bake quicker, remove them from the baking sheet and return them to the oven.

Once browned, remove from the oven and immediately loosen from the baking sheet. This will help keep them crisp rather than crumbly. They will continue to crisp as they cool.