Bring a pan of water to the boil, add the sliced potatoes and cook for 5-6 mins. Drain.

Meanwhile, beat the eggs together in a bowl with 1 tsp cold water and the parsley. Season.

Heat a pan and mist with cooking spray. Cook the onion for 5 mins, then add to the bowl with the eggs. Fry the Bacon for 1 1/2 mins, then add to the bowl.

Return the pan to the heat, mist with low fat spray and saute the mushrooms for 2 1/2 mins. Tip into the bowl, add the potato slices and stir together gently.

Tip the mixture back into the pan and cook on a medium heat for 4 mins. Meanwhile, preheat the grill. Top the frittata with the tomatoes and place the pan under the grill for 4-5 mins until the egg is set. Leave to rest for 5 mins, then slide the frittata onto a board and cut into 4 wedges. Serve 2 wedges each.