Heat your oven to 200ºC/Fan 180ºC/Gas 6. Line a roasting tin with baking paper. Add the whole, unpeeled shallots to the tin and cook for 30 mins.
Throw in the whole garlic cloves and cherry tomatoes and cook for 25 mins more or till the shallot skins are charred and tender when pierced with a sharp knife.
Once you’ve added the tomatoes to the shallots, cook the pearl barley. Rinse the barley well and tip into a small pan. Cover with cold water. Cover. Bring to the boil. Turn the heat down a little. Simmer for 25 mins till tender with a little bite.
Roughly chop the walnuts and toast them in a dry frying pan for a 2-3 mins till the edges darken. Tip into a bowl. Set aside to cool.
Whisk 1 tbsp balsamic and ½ tbsp olive oil together. Strip the rosemary leaves from the sprigs and finely chop. Stir into the dressing, reserving a pinch to garnish.
Drain the barley. Tip it into a bowl and add most of the rosemary dressing, reserving about 1 tsp of it for later. Season the barley with salt and pepper. Toss to mix.
Toss the rocket in the leftover dressing and divide between 2 plates. Pile the pearl barley over the top. Squeeze the shallots and garlic out of their skins and pile on top, along with the roast tomatoes. Scatter the walnuts over with the reserved rosemary leaves. Serve straight away.