In a skillet over medium-high heat, render the bacon until crisp and golden brown. Add the leeks and cook until soft. Add the spinach and cream and cook until the cream thickens. Season with salt and pepper.
Place 1 oyster on each shell. Top with a spoonful of the creamed spinach. Place the oysters onto a baking sheet and top each oyster with Parmesan. Bake for 5 minutes.