Preheat oven to 400°F (200°C). Line a standard 12-cup muffin pan with paper liners or grease thoroughly.

In a small bowl, combine the packed light brown sugar, ground cinnamon, and 2 tablespoons of melted butter. Mix with a fork until a thick, crumbly paste forms. Set aside.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until well combined.

In a separate medium mixing bowl, whisk the egg until lightly beaten. Add the milk, 1/2 cup of melted butter, and 1 teaspoon of vanilla extract. Whisk until fully incorporated.

Pour the wet ingredients into the dry ingredients. Stir gently with a rubber spatula until just combined. Be careful not to overmix; a few lumps are okay. Overmixing will result in tough muffins.

Fill each muffin cup about two-thirds full with the muffin batter.

Drop small dollops (about 1/2 teaspoon each) of the cinnamon swirl mixture evenly over the top of the batter in each cup.

Using a toothpick or a skewer, gently swirl the cinnamon mixture into the batter in a circular motion, being careful not to overmix.

Bake for 18-22 minutes, or until the tops are golden brown and a toothpick inserted into the center of a muffin comes out clean.

Let the muffins cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

While the muffins are cooling, in a small bowl, whisk together the softened cream cheese until smooth.

Add the sifted powdered sugar, 1 tablespoon of milk (or cream), and 1/2 teaspoon of vanilla extract. Whisk until smooth and creamy. If the glaze is too thick, add more milk 1/2 teaspoon at a time until desired consistency is reached.

Once the muffins are cooled, drizzle or spread the cream cheese glaze generously over the top of each muffin. Serve immediately or store.