Every summer, we have a picnic beside the River Dart in Devon, and we always have this thick Spanish omelette, packed with good things. Served either warm or cold, it is always delicious.
Cut open the red and yellow peppers lengthways and remove the seeds and stem. Slice the onions finely. Chop the garlic finely. Put the olive oil and butter into a large, deep, heavy-based frying pan – about