beer, bratwurst, and onions

Conclusion: I don't like boiling the onions in beer. If you cook down the onions afterwards, it concentrates the flavor of the beer in them. Instead, I would prefer an actual pan sauce. [1] [2]

boiling everything in beer

This is the most common way suggested.

• https://midwestniceblog.com/beer-brats-and-onions/
• https://www.onceuponachef.com/recipes/beer-braised-bratwurst-onions-beer-brats.html
• https://www.foodiecrush.com/beer-bratwurst-onions-recipe-oktoberfest/

bangers and mash

A traditional British dish is bangers and mash, often served with onion gravy.

• https://www.americastestkitchen.com/recipes/15332-bangers-with-onion-gravy [archive]
  • background: https://www.americastestkitchen.com/articles/6360-bangers-and-mash-needs-great-gravy [archive]
• https://www.all-thats-jas.com/english-bangers-mash/
• https://www.seriouseats.com/bangers-and-mash-with-onion-gravy-recipe-2
• A Guide to British Bangers