Prepare the Pan: Place a trivet in the Instant Pot inner pot and add 1 cup of water to the pot. Spray a 7-inch pan with a removable bottom with cooking spray and line it with parchment paper. Spray the parchment paper with cooking spray. 

Make the Batter: Bring about 1 inch of water to a simmer in a saucepan. Put the semisweet chocolate chips in a heatproof bowl and place it over the simmering water. Stir constantly until the chocolate is melted. Add the butter and continue stirring until the butter is melted and the mixture is well blended. Remove the bowl from the saucepan. Add the sugar and salt and stir to blend. Whisk in the the eggs, one at a time. Add the vanilla and whisk until smooth and well blended. Pour the batter into the prepared pan. 

Pressure Cook: Cover the top and bottom of the pan tightly with foil. Use a foil sling to lower the pan into the Instant Pot. Lock the lid in place and turn the steam release knob to the sealing position. Choose pressure cook/manual, high pressure, and set the timer for 30 minutes. The Instant Pot will take about 5 to 7 minutes to build pressure and begin cooking. When the time is up, let the pressure release naturally for 15 minutes. Carefully turn the steam release knob to the venting position to release any remaining pressure.

Cool the Cake: Remove the pan to a trivet and remove the foil. Let the cake cool, then cover it and refrigerate until it is thoroughly chilled. 

Remove the Cake: Slide a knife around the edge of the pan and remove the sides. Carefully slide a spatula under the cake to loosen it from the bottom; slide it onto a cake plate or platter. 

Finish and Serve: Dust the top with powdered sugar just before serving. Serve slices cold or at room temperature with a scoop of ice cream, a dollop of whipped cream, or whipped topping.