Preheat oven to 375 °F and prepare an 8-inch round cake pan with parchment and grease.
Using a double boiler, melt 8 ounces chopped dark chocolate, granulated sugar, brown sugar, and butter until smooth.
Remove from heat and cool slightly.
Add eggs one at a time, whisking thoroughly after each addition.
Whisk flour and salt together, then fold into the chocolate mixture with remaining 2 ounces chopped dark chocolate.
Pour batter into prepared pan and bake 20–25 minutes until the center sets and a toothpick comes out clean.
Cool in pan 5 minutes, loosen edges, then cool completely on wire rack.
Place cake ring mold lined with acetate on parchment-lined baking sheet.
Set cooled brownie on cake board inside ring mold.
Spread softened coffee ice cream evenly over brownie layer.
Cover and freeze 2–3 hours until firm.
Spread softened vanilla ice cream over coffee layer evenly.
Dollop chocolate fudge over vanilla ice cream, gently swirl with knife.
Cover and freeze 3+ hours or overnight for best results.
Remove ring mold and acetate before serving.
Slice cake with a sharp knife and serve immediately.
Store any leftovers well wrapped in the freezer.