Smoked mackerel and cabbage frittata

1 Heat the oven to 200 degrees.

2 Melt the butter with the olive oil in a non-stick oven-proof frying pan.

3 Add the onion and cabbage, then cook for five minutes over a gentle heat.

4 Add the potatoes and continue to cook for a minute or so.

5 Put the horseradish sauce into a bowl, crack the eggs on top and beat with the salt and pepper.

6 Turn the heat up in the pan, then add the eggs. Mix everything carefully together with a spatula, scraping the bottom of the pan in a gentle motion for a minute or two as the egg sets.

7 Place the pieces of mackerel evenly over the top of the eggs and scatter the cheese over everything.

8 Put in the oven and bake for 12 minutes or so, until the egg is set and the top is golden. You can turn this out or slice it directly from the pan. It is best eaten warm.