Start by making the broth. Add 6 quarts of water, chicken broth, onions, lemons, garlic, old bay seasoning, peppercorns, and bay leaves to a large stock pot. Bring this to a rolling boil.
Add red potatoes, ears of corn, and sausages to boiling water. Boil for 15 minutes, until potatoes become tender, but not mushy. Then add shrimp and cook for 5-8 minutes, until shrimp are pink. Reserve 1-2 cups of the stock.
Melt butter over medium low heat in a large sauce pan, then add garlic and cook until fragrant, about 3 minutes.
Then add cajun seasoning, old bay seasoning, onion powder, and salt. Add 1 cup of the reserved broth and simmer on low for 3-5 minutes, until sauce thickens. (For a thinner sauce, add 2 cups) Add freshly diced parsley and remove from the heat.
Pour on top of the boil and serve with bread, more melted butter, and hot sauce.
