I start by quartering my onion and slicing it into thin strips so it cooks evenly alongside the sausages. While I'm doing that, I set my skillet over medium-high heat and let it warm up properly. A properly heated pan is what gives the brats that deep golden color instead of a pale, steamed look.
Once the pan is hot, I add the vegetable oil and lay the bratwurst in carefully, leaving space between each one. I let them sear for a few minutes on one side before flipping with tongs to brown the other side too. This step locks in flavor and gives the casing that satisfying little snap when you bite in later.
With the brats nicely browned, I scatter the sliced onions into the gaps between the sausages. I let everything cook together for about two minutes, stirring occasionally, until the onions turn soft and slightly golden. This is also when my kitchen starts smelling incredible.
Next, I flip the brats one more time and pour the beer straight into the pan. I cover it immediately with a lid and drop the heat to low, letting everything simmer gently for around ten minutes. I flip the sausages halfway through so they cook evenly on both sides.
I always check that the internal temperature hits 160°F using a meat thermometer, but if I don't have one handy, I just slice into one sausage to make sure there's no pink left inside. This is the safest way to know your brats are fully cooked.
Once the brats are done, I pull them out of the pan for a minute, season the remaining onion sauce with salt and pepper, and let it reduce for a couple of minutes until it thickens slightly. Then I return the sausages to the pan, turn them through that flavorful sauce, and serve them immediately while they're hot.