1. Preheat oven to 350 degrees F. Grease 12 muffin tins well and dust with cocoa powder.
2. Sift together the flour, cocoa powder and baking powder and set aside.
3. In the bowl of a stand mixer with the whisk attachment in place, whisk together the egg, sugar and vanilla extract on high speed until foamy and slightly stiffened
4. Mix together the melted butter and vegetable oil in a measuring cup with a spout. Slowly add the oil and butter mixture to the egg mixture in a slow stream as the mixer continues to whisk.
5. Mix together the whipping cream and lemon juice and add slowly to the mixing bowl continuing to mix but at a reduced speed.
6. Fold in the dry ingredients by hand with a rubber spatula being careful not to over mix. Don't worry about lumps in the batter, they are fine. When the dry ingredients are almost incorporated, gently fold in the chocolate chips and cherries.
7. Spoon batter into well greased and cocoa dusted muffin tins. Top with the crumble topping.

To make the crumble topping

1. Pulse together all the crumble ingredients in a food processor or just rub together with your hands until crumbly. Press together the shortbread mixture in your hand and then break off small pieces over the top of the muffin batter in the pan.
2. Bake for 25 to 30 minutes at 350 degrees F or until a wooden toothpick inserted in the center comes out clean. Let the muffins rest in the pan for 5 minutes before turning them out onto a wire rack to cool completely.