Place a large heavy based pan over a medium heat. Add half the olive oil and when it’s hot add the sliced garlic and let it sizzle for a few seconds, then add the courgettes. Season with salt and pepper and place a lid on the pan.
Cook the courgettes slowly over a gentle heat, stirring regularly, for about 35 to 40 minutes, until they are lovely and soft and broken down. Remove the lid for the last 10 minutes of cooking. Take the pan off the heat and season again to taste with a little more salt and pepper.
Preheat the oven to 200C, or 180C fan. Slide a baking tray onto the lower shelf, this will help the soufflé rise steadily. Take a deep ovenproof dish and coat it generously with softened butter.
Dust the buttered dish with the polenta, tipping it around so every surface is lightly coated. Tap out any excess.
Place a pan over a medium heat and melt the butter until it’s bubbling. Stir in the flour and cook for a minute or so. Gradually whisk in the milk, a little at a time, until the sauce is smooth.
Take the pan off the heat and beat in the egg yolks, one at a time, until smooth and velvety. Stir in the goat’s cheese and most of the dill, reserving a little to finish. Fold through the soft courgettes and stir until everything is well combined.
In a clean dry bowl whisk the egg whites until they form soft peaks. Stir a spoonful into the warm mixture to loosen it, then gently fold in the rest, taking care to keep as much air in the mixture as possible.
Spoon the soufflé mixture into the prepared dish and smooth the top. Run the tip of a knife around the inside edge of the dish, this helps create a gentle rise. Scatter over the remaining dill and bake for 20 to 25 minutes, until golden and puffed, the centre still trembling slightly.
Serve immediately. Soufflés don’t like to stand about, so take it straight to the table and enjoy it while it’s at its most delicate and airy.
