Preheat the oven to 350°F and line 2 baking sheets with parchment paper.
Blend the cottage cheese and mashed banana together until completely smooth. The cottage cheese adds richness and structure, so the cookies taste like the best part of a banana bread loaf.
Pour the banana mixture into a large bowl and whisk in the melted butter, brown sugar and vanilla until smooth.
Add the flour, protein powder, cinnamon, baking soda and salt, and stir until combined. Fold in the walnuts and chocolate chips, then let the dough rest for 10 minutes so it thickens.
Scoop 2 tablespoon mounds of dough onto the baking sheets, spacing them 2 inches apart. Sprinkle the tops generously with turbinado sugar for a crackly bakery-style finish.
Bake for 12 to 14 minutes, until the tops spring back when lightly pressed and the edges are golden.
Cool on the baking sheets for 5 minutes, then move to a wire rack. Store in an airtight container for up to 3 days.