Heat oven to 350°F and line 18 muffin cups.
Whisk the flour, sugar, cocoa, baking soda, baking powder and salt in a large bowl.
Add the eggs, milk, oil and vanilla and mix until smooth. Stir in the hot coffee (the batter will be thin).
Fill liners two-thirds full and bake 18 to 20 minutes, until a toothpick comes out clean. Cool completely.
For the frosting, beat the butter until fluffy. Beat in the powdered sugar, caramel sauce, salt and vanilla until smooth.
Pipe or spread on the cupcakes and drizzle with more caramel.