1. Halve the red and yellow peppers and scoop out the seeds. Slice the peppers into thick strips. Trim the top off the aubergine and cut it into 1cm-thick slices. Peel the sweet potato and cut it lengthways into 1cm-thick slices. Peel the red onions and cut them into thin wedges. Slide the veg into a large dish or roasting tin, keeping the veg grouped by type. Season with salt and pepper, drizzle with 2 tbsp olive oil and toss till coated. Warm 2 large griddle or frying pans to a high heat. When the pans are hot, add the sliced veg in batches. Cook the veg for 3-4 mins on each side, till tender and slightly charred.
2. While the veg are frying, make the dressing. Peel and grate the garlic into a small bowl. Grate in the lemon zest and squeeze in the juice. Finely chop the mint leaves and add them to the bowl. Pour in 2 tbsp olive oil and add a pinch of salt and pepper. Stir well and set to one side.
3. When the veg are all cooked, set aside to cool. Meanwhile, halve the avocado and discard the stone. Scoop the avocado flesh out of its skin and chop it into1cm pieces. Spoon about half the pickled beetroot out of the jar and let it drain in a sieve or on some kitchen paper.
4. Sit the sourdough loaf flat on a board and slice off the top quarter – this will be the lid. Carefully scoop out the middle of the loaf, leaving the outside crust intact (see our tip for what to do with the scooped-out bread). To fill the loaf with a rainbow of veg, start by adding the roast red pepper in an even layer. Drizzle over a little dressing and crumble over a little feta (you’ll be doing this between each layer of veg, so drizzle and crumble sparingly). Next add the sweet potato and top with a little dressing and feta. Repeat with the yellow pepper, avocado, aubergine, beetroot and red onions.
5. When the loaf is filled, put the top quarter back on and press down firmly. Wrap the loaf snugly in food wrap and pop it into the fridge to chill overnight. If you’ve got something to weigh it down, like a couple of heavy jars or tins, sit those on top of the loaf – this isn’t essential but it’ll help compress the veg for easy cutting.
6. To serve, unwrap the loaf and slice into thick wedges.
7. Bread Winner
You can use the bread from the middle of your sourdough loaf to make crispy croutons. Tear it into smaller chunks, toss in a bowl with some olive oil, salt and pepper, then spread out on a baking tray and bake till golden.