Preheat your oven to 350°F and line a muffin tin
Make the blueberry jam by adding blueberries and sugar to a small saucepan over medium heat
Cook for about 15 minutes, stirring every few minutes, until thickened
Remove jam from heat and set aside to cool
Beat the cream cheese, sugar, and egg yolk on high speed for 2–3 minutes until smooth and creamy
Transfer cream cheese filling to a piping bag or set aside
In a large bowl, mix together melted butter, brown sugar, and granulated sugar until combined
Add the eggs and vanilla and mix until smooth
Stir in the milk and yogurt
Add the flour, baking powder, cornstarch, and salt, mixing until just combined
For the crumble, mix together melted butter, sugar, and flour using your hands until crumbly
Scoop the muffin batter into your prepared pan
Add a spoonful or pipe the cream cheese filling into the center of each muffin
Add a spoonful of blueberry jam on top of the filling
Top generously with crumble
Bake for 26–28 minutes, until golden and set
Let cool for about 20 minutes before serving
