Preheat Oven: Preheat your oven to 400°F (200°C). Grease each muffin cup with softened butter.
Prepare Cinnamon Rolls: Press each cinnamon roll into the greased muffin cups, spreading the dough up the sides to create a cavity for the apple filling. Be careful not to have too much dough at the bottom to ensure you have enough space for the filling.
Make Apple Pie Filling: Peel and thinly slice the apples, then dice them into 1-inch pieces. In a medium bowl, mix the apples with the remaining filling ingredients. Heat the mixture in the microwave, stirring occasionally, until the syrup thickens and the apples soften, about 2 minutes. You can also cook this mixture in a saucepan on the stove.
Fill Cinnamon Rolls: Using a slotted spoon, scoop the apple mixture into the cinnamon roll cavities, filling them to the top of the muffin tin.
Prepare Streusel Topping: In a separate bowl, mix the streusel topping ingredients until they form large crumbs. Generously mound the streusel on top of the apple filling, covering most of the tops.
Bake: Bake for 15 minutes, covering loosely with foil for the first 5 minutes. Rotate the pan halfway through baking to ensure even cooking.
Make Icing: While the rolls bake, whisk together the icing ingredients until smooth.
Cool and Drizzle: Let the rolls cool for 5-10 minutes, then drizzle the icing over the tops of the apple pie stuffed cinnamon rolls. Enjoy warm!