Make sure the stainless steel insert is in your Instant Pot. Butter the ramekins and set aside. Measure out flour and powdered sugar, by spooning each into a measuring cup. This ensures an accurate amount of flour used. Do not use unbleached flour.

Add 1 cup of tap water to the IP. Set the trivet (that came with your Instant Pot), inside.

In a medium mixing bowl, place butter (cut into squares) and chocolate. Microwave in 15-second intervals, until the butter is melted. Whisk until the chocolate melts with warm butter. The mixture should be glistening and smooth.

Add powdered sugar. If your powdered sugar is clumpy, sift it over the chocolate mixture, then whisk in. The mixture should be thick.

Add egg and egg yolk and vanilla and whisk well. Add flour and salt (for best result, sift right over the chocolate mixture) and gently fold in with a spatula. Do not overmix!

Divide the chocolate batter evenly among the ramekins. Place ramekins on trivet in the Instant Pot. Close the lid and set valve to "sealing" position. Newer models do it on their own. Make sure the IP is set to cook at HIGH pressure. Press "manual" or "pressure cook" button and set timer to 8 minutes. The IP will beep and start coming to pressure. It took 4 minutes for my Instant Pot to come to pressure.

When the timer is done, press the "cancel/off" button. Switch the valve to "venting" position to release the pressure.

When the pressure pin is down, carefully open the lid away from your face. Carefully, wearing oven mitt, remove ramekin from the IP. Cover each ramekin with a plate, flip over, tap the ramekin and gently remove. The cake should pop right out. Let it cool for a few minutes, dust with powdered sugar and serve.