Start by slicing the cabbage in half, and then slicing each half into strips. Wash and dry the cabbage strips.
Then, in the pre-heated pressure cooker, on medium heat, add the butter, onion, and bacon or pancetta.
Simmer, stirring occasionally, until the onions begin to soften (about 5 minutes).
Next, add the cabbage and beer. Close and lock the lid.
Turn the heat up to high and when the pot has reached pressure, lower the heat and cook 3 minutes at High pressure (or 5 minutes at Low pressure).
When time is up, release pressure and open the cooker.
Remove the cabbage to a serving dish immediately so it can stop cooking. Toss and serve!