01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or generously grease each cup.
02 - In a large mixing bowl, whisk together flour, granulated sugar, baking powder, baking soda, salt, and ground cinnamon until evenly combined.
03 - In a separate bowl, whisk eggs, whole milk, melted butter, and vanilla extract until fully incorporated.
04 - Add the wet mixture to the dry ingredients. Gently stir until just combined, taking care not to overmix the batter.
05 - In a small bowl, mix shredded mozzarella cheese with softened cream cheese until smooth.
06 - Spoon batter into each muffin cup, filling halfway. Place 1 tablespoon of cheese filling in the center, then cover with remaining batter until cups are about three-fourths full.
07 - Transfer muffin tin to the oven and bake for 18 to 20 minutes, or until a toothpick inserted into the edge comes out clean.
08 - While muffins bake, combine 1/4 cup granulated sugar and 1 teaspoon ground cinnamon in a bowl for topping.
09 - Remove muffins from the oven and let cool in the tin for 5 minutes. Brush tops with melted butter and sprinkle generously with cinnamon sugar.
10 - Serve muffins warm for optimal flavor and texture.