Remove the leaves and silks from the sweetcorn cobs. Stand the cobs upright. Run a knife down them to slice off the kernels. Chuck the kernels in a pan with a pinch of salt. Set aside.
Peel and chop the onion. Warm ½ tbsp oil in a deep frying pan or wok over a low heat. Add the onion. Season. Fry for 5-8 mins till soft. Stir often.
Halve the peppers. Scoop out and discard the seeds and white bits. Roughly chop the peppers. Peel and crush the garlic. Roughly chop the tomatoes.
Add the peppers to the frying pan. Fry for 3-4 mins till they start to soften. Add the garlic, tomatoes, half the olives and half the thyme leaves. Cook over a high heat for 3 mins, then turn the heat down and gently cook for 10 mins till thick.
This is your peperonata.
Pour 200 ml boiling water over the sweetcorn kernels. Bring to the boil. Turn the heat down and simmer for 5 mins. Drain the sweetcorn over a jug and save the cooking water. Return the sweetcorn to the pan. Add 2 tbsp of the butter.
Use a hand-held blender to blitz the sweetcorn with 50 ml of the cooking water to make a rough purée (see our tip if you don’t have a blender). Season. Gently reheat over a low heat till hot. Add a little more cooking water if it’s too thick.
Shred the lettuce. Mix it with the rest of the olives. Drizzle over ½ tbsp oil. Spoon the sweetcorn polenta into two bowls. Top with the peperonata and the rest of the thyme leaves. Serve with the salad.