How to Make It
Put butter in the Instant Pot and melt using the saute function. Pour half the butter into a bowl that can withstand a pressure cooker, then swirl and tilt to coat. Pour the rest of the butter into a bowl or beaker and wipe out the Instant Pot with a paper towel.
With a fork, immersion blender, or in a food processor, thoroughly whip together melted butter, eggs (use 2 for a looser custard and 3 for a more solid one), beer, and salt until frothy. Pour through a mesh strainer into greased bowl.
Pour 1 cup of water into the bottom of the Instant Pot, put a wire trivet in place, and place the bowl on the trivet. Seal the Instant Pot and press the "Steam" button. When the cycle is complete, manually release the pressure. Carefully remove the bowl and serve immediately.
Note: If you don't have an Instant Pot, place the bowl in a steamer or atop a trivet in a covered pot with an inch of water on a stovetop.