Preheat oven to 350 degrees. Combine all ingredients in a large bowl then mix to combine. Liberally spray a mini muffin tin with nonstick spray then scoop the quinoa mixture to the top of each cup. Bake for 15-20 minutes, or until the edges of the cups are golden brown. Let cool for 5 minutes before removing from the muffin tin and transferring to a cooling rack to cool.
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Notes
For regular-sized muffin tins: bake for 25-30 minutes (Note: I have not tested full-sized muffins myself, although several readers have left comments saying this works!)
To freeze: place baked cups on a baking sheet then freeze until solid and transfer to a freezer bag. Microwave for 20-40 seconds depending on how many you're reheating.