Rinse shrimp, clams, mussels, scallops, and crab under cold running water. Discard any clams or mussels with broken shells or that do not close when tapped. Pat seafood dry with paper towels. If crab legs are frozen, thaw in cold water and pat dry.

Prepare aromatics

Smash the garlic cloves with the flat of a knife. Slice the onion into thick rings and the lemon into thin rounds. Chop parsley and set aside a tablespoon for the finishing butter.

Build the Steaming Broth

In a large, heavy-bottomed pot or a wide steamer pot (with a tight-fitting lid), combine the chicken (or seafood) stock, white wine, and water. Add Old Bay seasoning, black peppercorns, bay leaves, and kosher salt. Stir to combine.

Add the smashed garlic, sliced onion, lemon slices, and thyme sprigs to the liquid. Bring the mixture to a gentle simmer over medium-high heat. Simmer uncovered for 6–8 minutes to allow the aromatics to infuse the broth.

Steam the Seafood

Reduce heat to medium. If using a steamer basket, place it over the simmering broth. If you don’t have a basket, arrange a heatproof rack or a layer of crumpled aluminum foil in the pot to keep seafood above most of the liquid.

Place the crab legs in the pot first because they take the longest to heat through. Cover and steam for 4 minutes.

Add clams and mussels in an even layer on top of the crab legs (or around them). Cover and steam for 4–5 minutes, until shells begin to open.

Add shrimp and bay scallops on top of the shellfish. Cover and steam for an additional 3–4 minutes, until shrimp are opaque and scallops are just cooked through. Check clams and mussels and discard any that remain closed.

If any items are still cool (thick crab sections), re-cover and steam for 1–2 more minutes. Total steaming time should be about 12–15 minutes from the first cover, depending on pot size and seafood thickness.

Finish & Serve

While the seafood finishes, melt the butter in a small saucepan over low heat. Stir in minced garlic, chopped parsley, lemon juice, and optional hot sauce. Warm until fragrant but do not brown. Keep warm until serving.

Using tongs or a slotted spoon, transfer steamed seafood to a large shallow serving bowl or platter, pouring any small amount of cooking liquid over the top for extra flavor. Sprinkle with the remaining chopped parsley and a squeeze of fresh lemon if desired.

Serve immediately with the garlic-lemon butter for dipping and crusty bread or corn on the cob to soak up the juices. Provide small forks or shell crackers for crab and bowls for discarded shells.