In a large bowl, combine the flour, sugar, baking powder, salt, and cinnamon (if using).
In a medium bowl, whisk the egg. Add the peanut butter and whisk until it's incorporated with the egg. Add the milk and mix until smooth. Dissolving the peanut butter in a separate bowl with the liquid ingredients prevents overmixing the batter, which leads to chewy pancakes.
Make a well in the middle of the flour bowl by pushing the flour to the sides and pour the liquid mixture. Gently combine the ingredients into a batter, mixing from the outside of the bowl in until no visible flour is left. Some clumps are ok.
Cook the pancakes:
Heat a non-stick pan or griddle over medium heat. Once hot, grease it. Immediately pour ¼ cup of batter per pancake. Use the back of the scoop or a spoon to spread and shape the pancakes into circles. The batter is thick and doesn't spread on its own.
Cook the first side for about 2 minutes, until the edges begin to look defined and bubbles form. Flip the pancakes over and cook the second side for a little less time. Remove them onto a plate, cover them to keep them warm or serve as you go. f
Serve and store:
Serve them warm, topped with your favorite toppings and syrups.
Refrigerate leftovers in an airtight container for up to 3 days or freeze for up to 3 months. Reheat in the microwave for 30 seconds to 1 minute, or in a toaster.