Preheat oven to 350°F (175°C). Grease a 9×13-inch pan and line with parchment paper.
Melt butter in a saucepan over medium heat. Stir in sugar until glossy and smooth.
Remove from heat, cool slightly, then whisk in eggs one at a time, followed by vanilla.
Sift flour, cocoa powder, and salt. Fold into the wet batter until just combined.
Pour batter into the pan and bake for 25–30 minutes until a toothpick comes out with moist crumbs. Cool completely.
Heat coffee and sugar in a saucepan, then stir in chocolate chips until smooth. Let cool.
Spread softened ice cream evenly over the cooled brownies.
Pour cooled mocha sauce over the ice cream, swirling or spreading evenly.
Freeze for at least 6 hours, or overnight, until solid.
Top with whipped cream and chocolate shavings or sprinkles. Lift with parchment to slice.