Espresso and Lime

0 Preheat your oven to 425 degrees 
1 In a large bowl, whisk 2 large eggs with 1/2 cup of vegetable oil, 2/3 cup of sour cream, 1/3 cup of whole milk or heavy cream and 2 teaspoons of vanilla extract until fully combined
2 Add 1/2 cup of granulated sugar and 1/2 cup of brown sugar and whisk until fully incorporated.
3 Combine 1 2/3 cups of all purpose flour, 1/2 cup of cocoa powder, 1 teaspoon of baking soda and 1/2 teaspoon of salt in a small bowl and then add to the batter
4 Mix until the wet and dry ingredients are just combined
5 Fold in 1 cup of dark chocolate chunks and set aside for now
6 Make the chocolate crumble by combining 1/2 cup of all purpose flour with 1/3 cup of brown sugar, 1/4 cup of granulated sugar, 3 tablespoons of cocoa powder and a pinch of sugar in a small dish. Drizzle 4 tablespoons of melted butter over the dry ingredients and use a fork to combine until you create a large crumble texture
7 Add cupcake liners to a cupcake tin and fill each cavity almost full of batter
8 Add a generous amount of chocolate crumble over the batter and gently press down to help the crumble attach to the batter
9 Optional: sprinkle with demerara or turbinado sugar
10 Bake the muffins for 5 minutes at 425 degrees and then reduce the ovens temperature to 350 degrees leaving the door closed and bake for an additional 16-18 minutes (Bake mini muffins for 10 minutes at 350 degrees)
11 Once the muffins feel set in the middle or a toothpick will come out mostly clean from the center of a muffin, carefully transfer the muffins onto a cooling rack
12 Store leftovers in an airtight container at room temperature or chill in the refrigerator