Preheat the oven to 350°F and line a baking sheet with parchment paper or a silicone baking mat.

In a medium mixing bowl, add the unfed sourdough starter and egg, and whisk until the egg is broken up and combined.

Add the peanut butter and optional pumpkin puree or applesauce, and stir until the mixture looks mostly smooth and creamy.

Stir in the rolled oats until evenly distributed throughout the mixture.

Add the whole wheat flour about 1/4 cup at a time, stirring after each addition, until a soft, slightly tacky dough forms and pulls away from the sides of the bowl.

If the dough feels very sticky, sprinkle in 1–2 tablespoons of additional flour; if it feels dry or crumbly, mix in 1–2 tablespoons of water, a little at a time, until it holds together.

Lightly flour a clean work surface, turn the dough out onto it, and knead gently 3–4 times until smooth and uniform.

Roll the dough out to about 1/4-inch thickness, dusting the top lightly with flour if needed to prevent sticking.

Use a small cookie cutter or knife to cut the dough into desired shapes or small squares, and place them close together on the prepared baking sheet.

Bake for 25–30 minutes, until the treats feel firm and the edges are lightly dried.

Turn off the oven and, for extra crunch, leave the treats inside with the door slightly ajar for 10–15 minutes.

Transfer the treats to a wire rack and cool completely before serving to your dog or storing.