½ cup unsalted butter, melted (plus more for greasing ramekins)
1 ½ cups mini bittersweet chocolate chips
2 eggs, room temperature
2 egg yolks, room temperature
½ cup granulated sugar
3 tbsp strong espresso, cooled
1/3 cup all-purpose flour
Pinch of salt
1 ½ cups water
4 tbsp Kahlúa (1 tbsp per serving for garnish)
Cocoa powder, for dusting
Notes
Melt the butter and bittersweet chocolate chips together in a microwave-safe bowl or over a double boiler until smooth. Stir in the espresso and let cool slightly.
In a separate bowl, whisk together the eggs, egg yolks, and granulated sugar until pale and frothy, about 1 minute.
Gently fold the melted chocolate mixture into the egg mixture until fully incorporated. Stir in the flour and salt, then fold gently until combined.
Grease four 7 oz. heat-proof ramekins with butter and lightly dust with cocoa powder. Divide the batter evenly among the ramekins, filling each about ¾ full.
Add 1 ½ cups of water to the Instant Pot and place the trivet inside. Arrange the ramekins on the trivet, stacking if necessary, with a piece of foil between layers to prevent sticking.
Seal the Instant Pot lid and set to Pressure Cook on High for 9 minutes. Once the cooking cycle is complete, allow the pot to natural release for 1 minute, then flip the valve to release any remaining pressure. Carefully remove the ramekins using tongs.
Let the lava cakes cool for 2-3 minutes. Add a scoop of ice cream in the ramekins, drizzle a tablespoon of Kahlua on each, and sprinkle with cocoa powder. Serve immediately.