Heat the olive oil in a large skillet over medium heat and add the garlic and chili flakes. Cook 1 minute until fragrant. Stir in the tomatoes, oregano, sugar, ¼ teaspoon salt and ⅛ teaspoon pepper. Simmer 5 minutes and then stir in the spinach. Cook another few minutes until spinach is wilted.
Divide the sauce between 4 ramekins or individual gratin dishes and make an indentation in the center of each one with the back of a large spoon. Crack an egg into the center of each ramekin being careful to keep the yolk intact (I prefer to crack the eggs into a separate bowl and then pour the eggs into the ramekins). Sprinkle 2 teaspoons cheese on top of each one. Place the ramekins on a baking sheet and bake in the oven for 20 minutes or until the egg whites are just set. Remove from oven and garnish with parsley. Serve warm.
Notes
Alternatively, you can cook the eggs together in an oven-safe skillet instead of dividing them into individual dishes.