I just used the cake mix extender recipe with a yellow mix and add vanilla pudding mix with it.
Then mix together:
3/4 cup light brown sugar
1 tsp ground cinnamon
3 Tbsp unsalted butter at room temperature
Whisk together br. sugar and cinnamon. Add butter until mixture holds together. Scoop half the batter into your liners and then sprinkle some struesel over that and then scoop remaining batter.
I filled and frosted with Bettercreme mixed with Smuckers Apple Cinnamon topping.