Heat oven to 350°F. Grease a 9×13-inch baking pan.
Whisk flour, sugar, cocoa, baking soda, and salt in a large bowl.
Stir hot coffee, oil, vinegar, and vanilla together in a measuring cup.
Pour wet mixture into dry ingredients. Whisk until smooth and thin.
Spread batter in the pan. Bake 28–32 minutes, until a toothpick shows moist crumbs.
Cool 10 minutes. Poke deep holes all over with a wooden spoon handle.
Warm condensed milk and hot fudge until pourable. Stir until glossy and smooth.
Pour fudge mixture evenly over the cake. Let it seep into the holes. Cool 30 minutes.
Beat cream cheese and powdered sugar until creamy. Slowly stream in cold cream.
Whip to medium peaks. Blend in peppermint and vanilla. Spread over cooled cake.
Scatter mini chips and chopped mint chocolates on top. Chill 1 hour before slicing.