Double Chocolate Crunch Muffins

Crunch topping:
2 tablespoons vegetable oil
1/4 cup unsweetened cocoa (regular, Dutch-processed, or a blend)
1/2 cup brown sugar (pack it tightly into the cup to measure)
1/4 cup all-purpose flour

Muffins:
1 cup all-purpose flour
3/4 cup whole-wheat flour (white whole-wheat, regular whole-wheat, or whole-wheat pastry flour)

1/4 cup unsweetened cocoa (regular, Dutch-processed, or a blend)
1/2 cup brown sugar (pack it tightly into the cup to measure)
1 teaspoon baking powder
1 teaspoon baking soda
1/4 teaspoon salt
1 cup warm water
1/4 cup vegetable oil
1 egg
1/3 cup reduced-fat sour cream (NOT fat free...NEVER fat-free)
1 teaspoon vanilla
1 tablespoon red wine vinegar (I know, this seems like a weird ingredient, but it has incredible tenderizing powers, and I 100% promise your breakfast will NOT taste like cleaning solution)

Additional ingredients:
1/4-1/2 cup mini semisweet chocolate morsels
nonstick cooking spray

Preheat oven to 400 degrees. Line a 12-spot muffin tin with cupcake liners and spray each lightly with nonstick cooking spray. (Yes, you need to do both these things.) For the Crunch Topping, stir the cocoa powder into the vegetable oil with a fork. Dump in the brown sugar and flour and blend with a fork just until crumbly. It should look like chocolate gravel. For the Muffins, blend the flours, brown sugar, cocoa, baking powder, baking soda, and salt in a large bowl with a fork or whisk. In a separate, medium-sized bowl, mix the remaining muffin ingredients (water through vinegar) with a fork or whisk. Dump the "wet" ingredients on top of the dry and mix together with a rubber spatula just until incorporated. Where muffins are concerned, lumps are good. Leave 'em in. Divide the muffin batter equally among your prepared cups (I use a spring-action ice cream scoop for this). Divide your prepared Crunch Topping equally among your muffins, pressing down slightly to ensure all your lovely chocolate gravel ends up baking into its muffin bases. Sprinkle each muffin with a few (or more) mini chocolate chips. Bake at 400° for 12-18 minutes or JUST until a toothpick inserted into the center of a muffin comes out with a few moist crumbs (not wet batter) clinging to it. Cool in the muffin tin on a wire rack for about 5 minutes before gently removing from the tin for consumption or to cool completely on the rack. Store airtight at room temperature for a day or two, or freeze for a month-ish