Preheat the Oven: Set your oven temperature to 350°F (175°C). Prepare a muffin tin by lining it with paper muffin liners or lightly greasing it.
Prepare the Crumb Topping: In a small bowl, whisk together the flour, brown sugar, and cinnamon until evenly mixed. Add in the softened butter and combine with a fork or your fingers until the mixture resembles coarse crumbs. Set this aside for later.
Mix the Dry Ingredients: In a large mixing bowl, combine the all-purpose flour, granulated sugar, brown sugar, baking powder, baking soda, salt, and ground cinnamon. Use a whisk to ensure all dry ingredients are thoroughly incorporated.
Combine the Wet Ingredients: In a separate bowl, whisk together the melted butter, eggs, cooled brewed coffee, and vanilla extract until well blended and smooth.
Incorporate Wet and Dry Mixtures: Gently pour the wet mixture into the bowl with the dry ingredients. Using a spatula, fold the ingredients together until just combined, being careful not to overmix. A few lumps in the batter are completely fine. If desired, fold in the chopped nuts at this stage.
Fill the Muffin Cups: Evenly distribute the batter into the prepared muffin cups, filling each cup about ¾ full. Generously sprinkle the prepared crumb topping over each muffin.
Bake: Place the muffin tin in the preheated oven and bake for 18 to 22 minutes. Muffins are ready when a toothpick inserted into the center comes out clean and the tops are golden brown.
Cool: Once baked, remove the muffins from the oven and let them sit in the tin for 5 minutes before carefully transferring them to a wire rack to cool completely.
Notes
Serve warm or at room temperature with powdered sugar on top.