Place the skillet into a cool oven, then preheat the oven to 350º F.
Transfer the drained sardines into a mixing bowl along with the tomatoes, onions, mushrooms, garlic powder, parsley, salt, and pepper. Stir the ingredients with a spoon, breaking the sardines down into flakes, until well mixed.
Remove the skillet from the oven and transfer the sardine mixture into the skillet, covering the bottom of the pan entirely. Place the skillet back into the oven and bake for 10 minutes.
Remove the skillet from the oven, and crack the eggs over the sardine mixture. Place the skillet into the oven and bake for 8-10 minutes, or until the eggs have set.
Remove the skillet from the oven, and top your Fisherman's Eggs with fresh baby arugula, your favorite hot sauce, and chili flakes. Serve immediately as is or with toast.