Step 1

Preheat oven to 450°F with oven rack 8 inches from heat. Heat oil in a large ovenproof skillet over medium-high. Add sausage, and cook, stirring to crumble, until browned and no longer pink, 6 to 7 minutes.

Step 2

Add marinara sauce and 1 cup water; cook until mixture boils, 2 to 3 minutes, stirring and scraping bottom of skillet to release any browned bits.

Step 3

Add ravioli, and cook, stirring often and gently, until sauce is thickened and ravioli is just tender, 3 to 5 minutes.

Step 4

Remove from heat. Transfer half of ravioli mixture to a medium bowl. Sprinkle ravioli mixture in skillet evenly with 1 cup of the mozzarella. Top evenly with remaining half of ravioli mixture; sprinkle evenly with remaining 1 cup mozzarella. Bake in preheated oven until mozzarella is melted and lightly browned, about 10 minutes. Sprinkle with basil leaves, and serve immediately.