Spray four 6-ounce heat-safe ramekins with cooking spray and then sprinkle with granulated sugar. Shake the sugar around the ramekin to coat all the sides and then shake out excess sugar into the trash or over the sink.
Pour 1.5 cups of cold tap water into the inner pot of the instant pot and place in a trivet or rack.
Chop the chocolate if needed into morsel size pieces. Slice the butter into several slices and then combine the chocolate and butter In a medium heat-safe bowl. Microwave for 45-seconds and then stir well. Microwave in additional 15-second intervals as needed to fully melt the chocolate. Once melted, stir in the espresso powder and set to the side to cool slightly.
In a large mixing bowl, mix together the 2 eggs, 2 egg yolks, powdered sugar, vanilla, and a pinch of salt until well combined and the sugar has dissolved into the egg mixture.
Slowly whisk in the melted chocolate to the egg mixture until combined. Fold in the flour until just incorporated into the batter.
Evenly divide the batter between the four ramekins, using an ice cream scoop for easy, even transfer. Cover each ramekin with foil.
Place the ramekins on the trivet, stacking carefully on top of each other to fit. You can use a separate rack to place on top of the first layer of ramekins if you have it. If not, just carefully stack the second layer on top of the first layer.
Using the manual or pressure cook button, set to cook for 5 minutes on high pressure.
Once cook time has elapsed let the pressure release naturally for exactly 5 minutes. Then do a quick release of any remaining pressure by carefully hitting the vent knob from sealed to venting using a long wooden spoon.
Carefully remove the ramekins from the inner pot and let sit for 2-5 minutes before serving.
To serve the lava cakes, run a knife around the edges of the ramekin and then invert onto a plate. Dust with powdered sugar and top with ice cream or whipped cream and serve immediately.
Chocolate: Use high-quality semi-sweet chocolate for the best flavor. If using a large chocolate bar, chop up the chocolate into small pieces.Espresso Powder: This is optional! The espresso powder helps to intensify the overall chocolate flavor, it does not add a coffee flavor to the dessert itself.Preparing in Advance: You can prepare the batter up to 2 days in advance. Cover tightly and refrigerate for up to 2 days. Allow the batter to come to room temperature before scooping into greased ramekins and pressure cooking.Storage: While Molten Lava Cakes are best served immediately, leftover cakes can be stored in the refrigerator for up to 3 days after they have been baked and cooled. Reheat for 1-2 minutes in the microwave before enjoying. You can also freeze unmolded cooled cakes for up to 3 months. Timing: This recipe only works with 6-ounce ramekins and COLD tap water, if you use lukewarm or warm water or a different size ramekin, the recipe will not turn out as desired. If you typically need to add time to recipes for success, cook for 6 minutes on high pressure. Gluten-Free Modifications: Swap out the all-purpose flour for a 1:1 gluten-free flour blend.What if the lava cake is not cooked through? If when you peel back the foil your lava cakes do not look solid on the sides or do have a jiggly set in the center, recover with foil and place back in the inner pot. Cook for an additional 1 minute on high pressure with a 2-minute pressure release. There is no need to change out the water in the bottom of the inner pot.High-Altitude Adjustment: If you live at a high altitude, be sure to adjust the recipe accordingly, using my High Altitude Instant Pot Guide.Baking Directions: You can use this same recipe and bake the ramekins in a 425 Fahrenheit degree oven for 12-14 minutes until the sides appear solid.