Place shredded zucchini into a clean tea towel, gather the edges and squeeze the excess liquid. Discard liquid.

Preheat the oven to broil. Whisk the mustard and eggs together until well combined.

Heat the olive oil in the base of 7-inch (base), 10-inch (top) non-stick ovenproof frying pan over medium heat. Add the onion, cook for 1 minute stirring occasionally, until soft. Add the zucchini and tomatoes, cook for 5 minutes until the vegetables have softened and the moisture has evaporated. Stir in the Swiss chard and half the cheddar cheese. Spread evenly over the pan. Dollop over the ricotta.

Pour over the egg mixture and allow the egg to run to the base. Cook for 4 minutes or until the egg is almost set. Sprinkle the remaining cheese.

Place the pan under the broiler for 2 to 3 minutes or until the top is set and lightly golden. Scatter over the parsley or basil. Season to taste with black pepper. Cut in half and serve with slices of toast.