Start by greasing your ramekins with a little butter to prevent the cakes from sticking. You can use 1 teaspoon of butter for each ramekin. Set them aside.
In a heatproof bowl, combine the chocolate chips and cubed butter. Microwave in 30-second intervals, stirring in between, until melted and smooth. Alternatively, you can melt them over a double boiler on the stove. Once melted, let it cool slightly.
In another bowl, whisk together the powdered sugar, eggs, and egg yolks until well combined. Add in the melted chocolate mixture and vanilla extract. Whisk until smooth.
In a separate bowl, sift together the cocoa powder, espresso powder, flour, and salt. Gradually fold the dry ingredients into the wet mixture using a spatula until just combined.
Divide the batter evenly among the prepared ramekins, filling each about halfway. Then, add 1 tablespoon of creamy peanut butter into the center of each ramekin and cover it with more batter. Leave some space at the top for the cakes to rise during cooking.
Pour 1 cup of water into the Instant Pot. Place a trivet in the pot and arrange the ramekins on top of it. Secure the lid and set the pressure valve to sealing.
Select the “Manual” setting and adjust the timer to cook for 10 minutes on high pressure. Once the cooking time is up, perform a quick release to release the pressure.
Carefully remove the ramekins from the pot using tongs or an oven mitt. Let them cool for a few minutes before serving. This allows the lava center to set just slightly without losing that ooey-gooey goodness.
To serve, run a knife around the edge of each cake to loosen it from the ramekin. Invert onto a plate and dust with extra powdered sugar for a beautiful presentation. Dive in and experience the molten peanut butter center!
