This recipe comes from Rebecca Seal's picturesque cookbook Lisbon: Recipes from the Heart of Portugal. Think of it as a Scotch egg minus the meat, or a deep-fried deviled egg, with a filling of parsley and white wine vinegar. The filling does not have mayo, like a traditional deviled egg, but the snack tastes very good dipped in a spicy mayonnaise. To make piri piri mayonnaise (for dipping), mix a little bit of piri piri sauce (or another hot sauce of your choice) to mayo and adjust for taste.
Place 4 of the eggs in a pan of cold water. Bring to a boil and simmer for 6 minutes. Remove from the hot pan and cool in cold water. Once cool enough to handle, peel off the shells, keeping the cooked eggs intact.
Gently cut each egg in half lengthwise and scoop out the yolks, setting the whites to one side. Place the yolks in a bowl with the parsley, olive oil, vinegar, salt, and some pepper. Mash to form a rough paste and taste; add more salt and pepper if you like.
Place a large deep pan over a high heat and fill it with the vegetable oil. Heat the oil until it reaches about 340° F on a pan thermometer, or if you don't have one, use the bread test: Once the oil is shimmering, drop in a cube of day-old bread. If the bread fizzes and browns in no less than 30 seconds, the oil is ready. (If it burns, turn the heat down.)
Spoon the yolk mixture back into the whites. Tip the flour onto a plate. Thoroughly beat the remaining egg in a bowl. Tip the breadcrumbs onto another plate.
Gently roll one of the stuffed egg halves in the flour, then dip it into the beaten egg, turning and rolling it to ensure it is well covered. Finally, roll it in the breadcrumbs. Repeat with two more of the stuffed egg halves.
Working in 2-3 batches, carefully lower the eggs into the hot oil and cook them for 2 minutes, until the crumb is golden brown. (The breadcrumb shells may splot if you cook the eggs for too long or at too high a temperature.) Remove, then repeat with the remaining eggs, keeping the fried eggs warm. Serve straight away with piri piri (or another spiced) mayonnaise, for serving.