In Epi's 3-Ingredient Recipes series, we show you how to make great food with just three ingredients (plus staples like oil, salt, and pepper). A hot knife is the easiest way to cut dense or frozen treats: Dip a sharp blade in hot water (or run under a hot faucet) and wipe dry before cutting. Repeat before slicing each piece for extra tidy edges.

1 (9") frozen pie shell, slightly thawed

6 ounces semisweet chocolate, chopped, divided

2 pints coffee ice cream

Preparation Preheat oven to 350°F. Prick bottom of pie shell all over with a fork. Bake until golden brown and dry, 20–25 minutes. Let cool completely. Melt half of chocolate (1/2 cup) in a medium heatproof bowl set over a medium pot of barely simmering water (bottom of bowl should not touch water), stirring occasionally, or in short bursts in the microwave, stirring in between bursts, until chocolate is melted and smooth. Using the back of a spoon, spread chocolate over bottom and sides of pie shell. Freeze until firm and dry, about 5 minutes. Cut ice cream pints in half with a serrated knife, remove packaging, then cut crosswise into 1" slices. Transfer to a medium bowl and let sit, stirring occasionally, until spreadable but not soupy, 5–10 minutes. Fill pie shell with ice cream; smooth top. Freeze until firm, about 1 hour. Melt remaining 1/2 cup chocolate in a medium heatproof bowl set over a medium pot of barely simmering water (bottom of bowl should not touch water), stirring occasionally, or in short bursts in the microwave, stirring in between bursts, until chocolate is melted and smooth. Using a fork, drizzle over pie. Freeze again until set, about 5 minutes. Transfer pie to a cutting board and let sit 10 minutes before slicing. Do Ahead Mousse can be made 2 days ahead; cover and chill.