Preheat an oven to 375 F and line a muffin tin with liners. Combine all the ingredients for the streusel topping in a medium bowl. Use a fork or your hands to fully incorporate the butter into the flour. There should be no residual dry flour at the bottom of the bowl. Set mixture aside.
Combine all the dry ingredients, by combining brown sugar, baking powder, baking soda, and kosher salt together. Whisk it to combine.
Combine all the wet ingredients, by whisking together whole milk, orange juice, melted butter, vanilla paste, fiori di sicilia (if using), and the eggs until combined.
Pour the wet ingredients into the dry ingredients, then fold the ingredients together using a rubber spatula, stopping when the mixture has just combined. Do not overmix.
Use an ice cream scoop, to fill each liner ½ full with batter. Top each with streusel (it will be a lot of delicious streusel topping). Bake the muffins for 10 minutes and then lower the oven temperature to 350 F and bake for another 8 minutes. Allow the muffins to cool completely while you make the cream filling.
To make the cream filling, beat room temperature cream cheese, powdered sugar, and vanilla paste in the bowl of a stand mixer fitted with a paddle attachment, about 2-3 minutes. Fill a piping bag fitted with a long, round piping tip with the filling.
Press the piping tip into the center of each muffin, squeeze a generous amount of cream filling into each muffin. You can wipe the piping tip with a paper towel in between each muffin as necessary.
Tips
Using perfectly room temperature cream cheese will result in the most luscious vanilla cream filling.
To make muffin liners with parchment paper, cut 4” x 4” squares and press them into the muffin pan using a small tin can or cup. Fill each liner as you normally would.
