Preheat the oven to 375 degrees F (190 degrees C). Line a 12-cup standard muffin tin with paper or coat with nonstick spray. Make sure to also line a baking sheet with parchment paper or aluminum foil and reserve.
Make the streusel: In a medium bowl, whisk in together the granulated sugar, light brown sugar, and cinnamon.
Add the melted butter and whisk until just combined. Then, mix the flour (if needed by hand) until the mixture is moist.
Transfer the streusel topping to the prepared baking sheet and spread it out to let it dry while making the muffin batter. Make sure to crumble in small and big chunks. Reserve.
Make the muffin batter: In the bowl of an electric mixer, add the dry ingredients (flour, light brown sugar, baking powder, ground cinnamon, and baking soda. Whisk on low until well combined.
Then, add the wet ingredients: milk, Greek yogurt, and eggs. Beat until just combined and thick.
Pour half of the batter evenly into the muffin tins (about 1 ½ tbsp each tin cup). Reserve.
Make the cream cheese filling: In a medium bowl, beat softened cream cheese with sugar and vanilla until combined and smooth. Then, top the center of the muffins with the cream cheese filling (a little less than 1 tbsp and no need to spread out). Next, spoon the remaining batter over the filling making sure to form an even layer. If needed, gently spread out the batter. Top the muffins with the streusel topping, pressing the mixture into the batter. If you don’t press it, chunks of streusel will fall all over the tin while muffins are baking.
Bake the muffins for 18 to 22 minutes, or until a toothpick inserted into the center comes out mostly clean. Remove the muffins from the oven and let them cool down for 5 minutes before serving.
Meanwhile, make the glaze (optional): Whisk powdered sugar, milk, and vanilla together in a bowl until homogeneous, smooth, and without lumps. If too thick to drizzle over the muffins, whisk in a little more milk. If too thin, whisk in a little more powdered sugar.
Then, drizzle over the muffins, let sit for 5-10 minutes, and serve.