Stir together the brown sugar, granulated sugar, cinnamon, flour, salt and butter until crumbs form.
For the coffee cake muffins:
Preheat oven to 325ºF (170ºC). Line a muffin tin with baking cups and spray lightly with vegetable cooking spray.
In a medium mixing bowl whisk together the flour, baking powder, baking soda, salt and cinnamon until combined. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat together the butter, oil, and sugar until fluffy. Add the eggs, one at a time, beating well after each addition. Mix in the sour cream then slowly add the dry ingredients until just combined.
Divide half of the batter between the muffin tin cups, then top with half of the streusel mixture. Cover with the remaining batter followed by the remaining streusel mixture.
Bake until a toothpick inserted into the center of a muffin comes out clean, about 25 minutes. Remove to a rack to cool.