Drain both cans in a colander and rinse the snails under cold water for 20 to 30 seconds. This removes the briny canning liquid. Pat them very dry with paper towels, because extra water will thin the butter. If the snails smell tinny, simmer them in water with a bay leaf for 5 minutes, then drain and dry them again. This step is optional.

In a medium bowl, mash the softened butter with the garlic, shallot, parsley, lemon juice, wine, salt, pepper, and nutmeg. Use a fork until it looks smooth and evenly speckled with green. Taste a tiny bit. It should be bold, because the snails and mushrooms will mellow it. Add salt only if needed.

Heat the oven to 400°F. Wipe the mushrooms with a damp paper towel (don't soak them) and pop out the stems. Arrange the caps hollow-side up on a rimmed baking sheet, close together so they stay upright. Nestle a crumpled strip of foil under any that wobble.

Put about 1/2 teaspoon of garlic butter into each cap, press one snail inside, then top with another 1/2 teaspoon of butter so the snail is fully covered. Covered snails stay juicy instead of drying out. If using breadcrumbs, sprinkle a pinch over each cap.

Bake for 12 to 15 minutes, until the butter is bubbling hard and the mushrooms look tender and slightly shrunken. For a deeper golden top, broil for 30 to 60 seconds, watching closely. Let them sit for 2 minutes, because the butter is very hot. Serve with sliced baguette to soak up every drop from the pan. Lori's Tip: Canned snails vary in sodium, so use unsalted butter and wait to add salt until you've tasted the finished garlic butter. The garlic butter can be mixed up to 3 days ahead, which makes assembly a 10-minute job on the day you serve it.