Cook and cool the quinoa: If you don’t have leftover quinoa, cook 1/2 cup dry quinoa with 1 cup water.
Simmer, covered, until tender and water is absorbed, 15 minutes. Fluff and cool completely.
Prep your pan and oven: Heat the oven to 350°F (175°C). Line a large baking sheet with parchment paper.
Make the wet base: In a large bowl, whisk eggs.
Stir in mashed banana, nut or seed butter, maple syrup, melted coconut oil, and vanilla until smooth.
Add the dry ingredients: Stir in oats, cooked quinoa, cinnamon, baking powder, and salt. Fold until everything is well distributed.
Stir in mix-ins: Fold in about 1 cup of your favorite add-ins. Keep total add-ins around this amount so the cookies hold together.
Scoop and shape: Use a heaping tablespoon or a 2-tablespoon scoop to portion dough onto the lined sheet.
Gently flatten each mound to about 1/2 inch thick—these don’t spread much.
Bake: Bake 12–16 minutes, until set around the edges and lightly golden underneath. Centers should feel firm but still soft.
Cool completely: Let the cookies rest on the sheet 5 minutes, then transfer to a rack to cool. They firm up as they cool.