Lightly grease a baking sheet with half the olive oil and preheat the oven to 190C/375F. On three small plates, put the flour, some of the egg (or substitute), and some of the breadcrumbs. (Not all at once, and not all on the same plate!) Slice your courgette into rounds ~1/4″ or 1/2cm thick. Dip them in flour until they’re lightly coated, then into your egg-stuff until they’re wet all over, then into the breadcrumbs until they’re covered. Lay each on the greased pan, then move on to the next. When you’re done, drizzle the other half the olive oil (or if you have an oil sprayer, use that, it’s easier) over the top of the breaded rounds. Bake for 15m, then flip and raise the heat to 220C/425F and bake for another 15m.
When they’re done, layer them onto a microwave-safe plate, with pasta sauce and mozzarella between layers (on a cake plate, I got three layers, but you might get more or less depending on the sizes of the plate and the courgette). Top with more sauce and mozzarella, and microwave to melt cheese (~1:30), because I’m a lazy fuck and don’t think I need to dirty another pan to re-bake ONE COURGETTE. If you’re making a larger batch, though, it might be worth using a bread pan, tart pan, or lasagne pan and baking it again until the cheese melts (~7m).This same method can be used with aubergine, and probably other similarly-textured vegetables I can’t think of right now.