Step 1

Preheat oven to 425 degrees F. Line a baking sheet with rock salt or balls of foil to cradle the oysters.

Step 2

To shuck oysters, place flat-side up and grip with a towel or gloved hand, leaving the hinged end exposed. Push the tip of an oyster knife between the top and bottom shells just adjacent to the hinge. Twist the knife until the top shell releases. (Keep the oyster level so the briny liquor stays inside the bottom shell.) Gently slide the knife along the inside of the upper shell, disconnecting the oyster from the shell; discard the top shells. Arrange the shucked oysters in their bottom shells on the prepared pan.

Step 3

Heat oil in a large skillet over medium-high heat. Add spinach and cook until wilted, about 1 minute. Transfer to a colander and press to remove excess water, then transfer to a clean cutting board and finely chop.

Step 4

Add butter and garlic to the pan. Cook over medium heat, stirring, until soft and fragrant, about 30 seconds. Add the spinach and jalapeño; stir to coat. Remove from heat.

Step 5

Combine Parmesan, panko and ground pepper in a small bowl. Spread a heaping teaspoon of the spinach mixture over each oyster. Sprinkle with about 1 teaspoon of the Parmesan mixture.

Step 6

Bake until the oysters are cooked and the tops are golden brown, 10 to 12 minutes. If desired, turn on the broiler for the last 2 minutes to brown the tops. Serve with lemon wedges.