In skillet, toast muffin cubes in 2 tbsp. oil over medium-high, turning often, 6 to 8 minutes. In bowl, toss spinach, vinegar and 1/4 cup oil; season. In another skillet, fry eggs in 2 tbsp. oil over medium, 3 minutes; season. Divide spinach among 4 shallow bowls; top with egg, croutons and Parm.