Preheat oven to 425°F (220°C). Line two 12 muffin pans with 24 muffin liners. Set aside.
Muffins: In a small bowl, mix flour, baking powder, and salt until combined. Set aside.
In a large mixing bowl, using an electric mixer fitted with a paddle or whisk attachment, beat together cream cheese, brown sugar, and vanilla* on medium speed until creamy for about 2 minutes. Add eggs, milk, and butter and mix until smooth and evenly combined. Add dry ingredients to wet ingredients and whisk slowly just until no lumps remain. Gently fold in blueberries. Set aside.
Streusel: In a small bowl, add flour, sugar, cinnamon, and butter. Mix together with your fingers until you have a crumbly mixture.
Spoon batter into the prepared liners until ¾ to almost full and sprinkle with the streusel evenly. Bake at 425°F (220°C) for 5 minutes then lower the temperature to 350°F (175°C) and bake additional 13-15 minutes or until a toothpick in the center comes out clean. Let cool to room temperature before serving. Store leftovers in an airtight container in the fridge for up to 3 days.