Line a muffin tin with 10 liners and set aside. It helps to spray the liners with oil, as the protein powder can cause the batter to stick after baking.
In a large mixing bowl, whisk together all wet ingredients. Whisk in the dry ingredients, aside from the chocolate or nuts.
Fold in the nuts or chocolate chips. Scoop into the prepared tray, filling each liner about 3/4 of the way up. Bake for 18 - 24 minutes or until a toothpick comes out clean.
Remove from the oven and let cool completely before serving.