Preheat oven to 425°. Grease muffin tin or add cupcake liners & set aside.
Make Cream Cheese Filling: Soften cream cheese (10-20 seconds in microwave) & make filling. In a small bowl, add cream cheese, 1/4 tsp cinnamon & brown sugar. Whisk or mix together until incorporated. Set in fridge or to the side. I like when it is cold and easier to crumble.
Make Coffee Cake Topping: In another small bowl, add 4tbs melted butter & 1/4 cup flour, brown sugar, white sugar & 1/4 tsp cinnamon. Mix until combined. Set aside.
Whisk together Dry Ingredients: In a bowl, whisk together dry ingredients: flour, baking powder, baking soda, salt. In a large mixing bowl, add eggs & sugar. Whisk or beat together until eggs are a little paler & sugar is combined (about 1 minute). Next, add vanilla, sour cream & milk & melted cream cheese. Whisk again.
Add dry ingredients to wet: leave a little flour in the bowl to toss the blueberries- to wet ingredients and mix until just incorporated. Do not over-mix. Finish mixing in with rubber spatula. Toss blueberries in remaining flour & add blueberries and flour to batter. Remove cream cheese & topping from fridge or freezer.
Fill Tins & Crumble Topping: Scoop about 2 tablespoons (I love a 2tbs cookie scoop) muffin batter into each muffin tin. It may be sticky! Add about 1/2 tbs or little scoop of cream cheese filling into center of each muffin. Spread it out or swirl it out if you want more of a swirl and less of a center. Top with the rest of the batter. Add the rest of the batter on top of each scoop of cream cheese. You may not use it all see note*. Crumble the coffee cake topping over the muffins. It may overflow and that is okay (& welcomed). Use it all! Bake 15-20 minutes until golden and toothpick comes out clean. Let cool in tin 10 minutes before removing to cool on a wire rack. Serve warm or fully cooled.