1 Preheat oven and prep muffin tin: Preheat oven to 350°F with a rack in the middle position. Prepare a muffin tin with cupcake liners.
2 Whisk dry ingredients: In a large bowl, vigorously whisk together the flour, cocoa powder, sugar, baking soda, and salt until there are no visible clumps (cocoa tends to clump up).
3 Mix wet ingredients: In a separate bowl, mix together the coffee (or water plus coffee granules), vinegar, vanilla extract, and olive oil.
4 Pour the wet ingredients into the dry ingredients and stir only until they just come together. Do not over-beat! The mixture should be thin and rather lumpy.
5 Ladle the batter into the cupcake liners, filling them about two-thirds of the way full.
6 Bake: Place in oven and bake at 350°F for 18 to 20 minutes, until a bamboo skewer inserted in the center comes out clean.