Preheat oven to 180°C. Heat 1 tbsp oil in a non-stick frying pan over medium-high heat, add sausage meat and stir occasionally for about 3 minutes until browned, add kale and mushrooms to pan, season to taste with salt and freshly ground pepper and stir occasionally for about 2 minutes until kale just wilts and mushrooms are just tender. Transfer to a bowl, squeeze over lemon juice and toss to combine.
Whisk eggs, cream and lemon rind in a bowl to combine, season to taste with salt and pepper . Wipe out pan with paper towels, place over medium-high heat, add butter and remaining oil and cook until butter foams. Add egg mixture and cook, pulling mixture from sides of pan into the centre as it cooks, tilting the pan to let uncooked mixture run into the empty space, until softly set (2-3 minutes). Remove from heat, scatter with sausage mixture and feta, then bake in oven for a couple of minutes to just warm through. Serve hot, scattered with parsley and spring onion.
This omelette is also great the next day as leftovers - pack with a simple green salad and a dollop of tomato relish for a very tasty portable lunch
You could use a spicy beef sausage in this recipe for even more flavour