Preheat the oven to 425˚F (220˚C).

In a large pot, add 3 quarts of water and 1 tablespoon of salt and bring to a boil. Add the baby potatoes, then reduce heat to medium high and cook the potatoes for 13-15 minutes, until just fork tender. Drain in a colander and set aside. 

While the potatoes are cooking, make the sauce. In a medium-sized pot over medium heat, add ¼ cup of butter. Once melted, add the onion and garlic and sauté for 4-5 minutes, until the onions are translucent.

Add in the remaining butter, stirring until melted. Add the beer, lemon juice, parsley, and the Old Bay seasoning, whisking well. Remove from heat and set aside. 

In a very large mixing bowl, add the shrimp, sausage, corn pieces and potatoes. (If you don't have a large enough bowl, use a large pot.) Whisk the sauce again, then pour over all of the ingredients and toss until everything is well coated. (Toss gently as to not break up the potatoes!)

Divide the mixture between two sheet pans, spreading everything into an even layer. Bake for 18-20 minutes. If you're using two oven racks, swap the baking sheets halfway through and give them a quick stir. 

Serve straight from the sheet pans, or transfer to a large platter or bowl. Enjoy!