Combine first 6 ingredients in medium bowl; set aside.
Working with 1 won ton wrapper at a time (cover remaining wrappers with a damp towel to keep them from drying), spoon about 1/2 tablespoon spinach mixture into center of each wrapper. Moisten edges of wrapper with egg white; bring 2 opposite corners together. Pinch edges together to seal, forming a triangle.
Place each wrapper on a baking sheet sprinkled with cornstarch Cover ravioli with a damp towel to keep them from drying.
Bring 4 quarts water just to a simmer in a large Dutch oven. Add 8 ravioli; cook 2 minutes, stirring once. Remove ravioli from pan with a slotted spoon; keep warm. Repeat procedure with remaining ravioli. Top ravioli with marinara sauce and Parmesan cheese.