Melt the butter in a large skillet over medium-high heat. Add the garlic and shallot, and sauté until soft and fragrant – about 2 minutes.
Pour half of the melted butter mixture into a small bowl and combine with the breadcrumbs. Toss to combine and set aside.
Add the baby spinach to the butter in the skillet. If it does not all fit, just let it cook, and then add more. Season with salt and toss until wilted. Slowly stir in the cream and let reduce for a minute before removing from heat.
Carefully place the oysters on a baking sheet. Spoon a small amount of the spinach mixture onto each oyster, then top with about 2 teaspoons of the breadcrumb mixture and a small pinch of Parmesan cheese.
Place in oven and bake until oysters have plumped up- about 15 minutes.
Remove from oven and serve immediately with lemon wedges and hot sauce, if desired.