Position rack in top third of oven and preheat to 450°. Add garlic, spinach, green onions, parsley, lemon juice, butter, and Pernod to a food processor and pulse until finely chopped.
In a medium bowl combine, panko, Parmesan, and oil.
Sprinkle coarse salt over large baking sheet to depth of 1/2". Arrange oysters in half shells in salt. Divide spinach mixture among oysters and sprinkle with Parmesan mixture.
Bake until spinach mixture is bubbling and panko is deeply golden, about 8 minutes.