Start by preparing all your ingredients: cut potatoes into 1-inch chunks, slice kielbasa into 1/2-inch coins, cut corn into 3-inch rounds, mince 8 cloves of garlic finely, chop parsley, and halve the lemon. While prepping, melt 8 oz unsalted butter in a small saucepan over low heat with the minced garlic and 3 sprigs fresh thyme. Let this infuse gently for 5-7 minutes, stirring occasionally, until fragrant and the garlic becomes golden but doesn't brown—this creates a silky, flavorful sauce that's the heart of the dish.

Fill a large pot (at least 8-quart capacity) with water and bring to a rolling boil. Add the whole onion, garlic bulb (sliced horizontally to expose cloves), 1 lemon cut in half, 2 tablespoons Old Bay seasoning, 1/4 cup Cajun seasoning, and a generous pinch of salt. Let this simmer for 2-3 minutes so the aromatics and seasonings infuse into the water and create a flavorful base—this is what gives the shrimp boil its signature taste.

Add the prepared potato chunks to the boiling seasoned water and let them cook for 5-8 minutes until they're just starting to become tender but still hold their shape. I like to test one with a fork to ensure they're cooking at the right pace. Starting potatoes first is crucial because they take longer than everything else and need a head start to finish cooking at the same time as the other ingredients.

Once the potatoes have been cooking for about 5-8 minutes, add the corn rounds and kielbasa coins to the pot. Stir gently and let everything cook together for 2-3 minutes, allowing the kielbasa to warm through and the corn to start softening while the potatoes finish cooking.

Add the shrimp to the pot and let everything cook together for 3-4 minutes until the shrimp turn pink and opaque—don't overcook or they'll become rubbery. Once done, carefully drain all the water using a colander, reserving the cooked ingredients. Transfer everything to a large serving platter or bowl, removing and discarding the whole onion, garlic bulb, and lemon halves from the boiling base.

Pour the warm garlic butter sauce from Step 1 over all the cooked ingredients, gently tossing to coat everything evenly. Squeeze fresh lemon juice from the half lemon over the top, sprinkle with the chopped fresh parsley, and add extra salt if needed. Serve immediately while everything is hot and the butter is flowing—this is a dish best enjoyed family-style right from the platter.