Preheat the oven to 350 degrees F. Line your muffin pan with your paper liners and set aside until ready to use. In a small bowl, combine everything for your crumb topping, except the butter, and stir. Pour in the melted butter, then, using a fork or your hands, mix until you have coarse pea-sized crumbs. Set aside.
In a separate bowl, combine the brown sugar and cinnamon, mix, and set aside.
Then, in a medium bowl, combine all the ingredients for the cream cheese filling, and mix(or beat with an electric mixer at low speed) until smooth and creamy. Set aside
In a large bowl, combine the flour, baking powder, salt, cinnamon, white sugar, and brown sugar, and whisk to combine.
Then, in a separate large mixing bowl, combine the vanilla extract, melted butter, eggs, sour cream, and whole milk, and whisk to combine.
Pour the wet ingredients into your dry ingredients/flour mixture. And fold to combine using a rubber spatula. The batter is supposed to be very thick, but if you are having trouble mixing it, you can add another splash of milk. Just be sure to keep in mind that muffin batter isn’t supposed to be smooth; a few lumps are okay!
Once mixed, divide roughly half of your muffin batter between your six muffin cups, using the back of a spoon, gently spread the batter out so it’s even, then use your spoon to create a well in the middle of each muffin cup. This helps create room for your cream cheese filling.
Next, divide your cream cheese mixture among your muffins, doing your best to keep the filling in the center of the muffin. Sprinkle the cinnamon sugar over the top of the cream cheese filling, doing your best to keep it evenly divided among all six muffins.
Then divide your remaining muffin batter between your muffin cups, and gently spread it out with the back of a spoon. You want the muffin batter to cover the cream cheese/cinnamon sugar, but you don’t want to squash the cream cheese filling out of the muffin.
Finally, sprinkle your crumb topping over the muffins, and place the muffins in your preheated oven.
Bake for 15-20 minutes or until a toothpick inserted into the center of the muffin comes out clean. (see notes)
Allow the muffins to cool to almost room temperature before removing them from the pan.
Serve and enjoy!