In a medium bowl, combine the flour, protein powder, baking powder, pumpkin spice, cinnamon, and salt. Set aside.
In a large bowl, whisk the eggs. Add the milk, pumpkin puree, and melted butter. Combine until smooth.
Slowly add the dry ingredients to the wet ingredients in the bowl, mixing from the outside in until there's little to no visible flour left. If you're adding chocolate chips (½ cup), fold them into the batter now.
Cook the pancakes:
Heat a large non-stick pan (or griddle) over medium heat. Once hot, grease the surface with butter, oil, or spray. Immediately, pour ¼ cup of pancake batter onto the greased pan. This batter is thick and doesn't spread, so use the back of the scoop or spoon to spread it out.
Cook the first side for about 2 minutes, until the edges begin to look defined and bubbles form. Flip the pancakes over and cook for another 2 minutes. Avoid pressing down with a spatula; this removes air bubbles and makes the pancakes dense. Remove the pancakes from the pan onto a plate or keep them warm in a 200F oven while you cook the rest of the batch.
Serve & store:
Stack them up and top them with your favorite toppings and syrup.
Store leftover cooked pancakes in an airtight container in the fridge for up to 3 days, or freeze for up to 3 months. You can also refrigerate unused batter, covered, for up to 2 days. You must let it come to room temperature on the counter before cooking. Cold batter is thick and yields dense pancakes.
Notes
Vanilla and unflavored protein powder work best when making pancake batter.
Plant-based proteins work, but you'll often need to add about 2 to 3 tablespoons of additional liquid to thin out the batter, but no more than ¼ cup, or the batter will be runny.