Pre-heat your oven to 180°C. Heat the butter and olive oil in a fry pan and add in the sliced onions. Cook until golden and sizzling, then remove and set aside.
To make the frittatas, combine together in a bowl the eggs, cream, onions, Ocean Trout, parsley, dill and seasoning. Heat a lightly oiled heavy non-stick pan and pour in the mixture. Stir in the sides gently as it cooks and when half set, place into a hot oven (set at 180°C) until golden and cooked.
To make the dressing, combine together the vinegar, olive oil, mustard and seasoning. Layer the salad ingredients into a serving plate, finish with a little dressing and present with a portion of the frittata.