Creating these Cinnamon Roll Muffins is a delightful experience! Here’s how to do it step by step:

1. Preheat the Oven: Preheat your oven to 375°F (190°C) and line a muffin tin with paper liners or grease them well.
2. Mix Dry Ingredients: In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, salt, and 1 teaspoon ground cinnamon.
3. Combine Wet Ingredients: In another bowl, combine the milk, melted butter, egg, and vanilla extract. Whisk until well combined.
4. Combine Mixtures: Pour the wet ingredients into the dry ingredients, stirring until just combined. Be careful not to over-mix; some lumps are okay.
5. Prepare Cinnamon Filling: In a small bowl, mix the brown sugar with 2 teaspoons of ground cinnamon. If using nuts, add them to the mixture as well.
6. Fill Muffin Tins: Spoon about 1 tablespoon of batter into each muffin cup, then sprinkle about 1 teaspoon of the cinnamon filling on top of each.
7. Top with More Batter: Add another tablespoon of muffin batter over the cinnamon filling to cover it. Use the remaining filling to sprinkle on top.
8. Bake: Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
9. Cool: Let the muffins cool in the tin for about 5 minutes. Then, transfer them to a wire rack to cool completely.
10. Optional Dusting: For a lovely presentation, dust the top with powdered sugar before serving.

These straightforward steps will guide you in creating addictive and delightful Cinnamon Roll Muffins with ease.