Set a large pot over medium heat and add 1 tablespoon of butter. When the butter is melted, add the sausage and onions. Cook for 6 minutes, until the sausage slices are browned on both sides. Transfer the sausage to a plate and set aside; leave the onions in the pot.

Add the beer, water, potatoes, spice mix bag, and bay leaves. Cover the pot and bring to a rolling boil for 8 minutes, until the potatoes are almost fork-tender.

Carefully add the corn cobs to the boiling water and continue boiling for 5 minutes. Then, add the green beans and boil for an additional 5 minutes until they are crisp-tender.

Return the sausage to the pot, then immediately pour everything from the pot into the colander to drain the cooking water.

Set a small saucepan over medium heat and melt the remaining 1/2 cup of butter. Stir in the parsley, garlic, pepper, and salt until well combined. Adjust seasoning to taste.

To serve, pile the Lowcountry Boil onto a large serving platter or pour it out directly onto a newspaper-covered table for a traditional presentation. Drizzle with the melted butter and dig in!