Turn your hob to a low-medium gas flame (no hob? Skip to our tip). Slice a couple of 1 cm thick slices from the bottom of the aubergine. Set them aside. Stick the rest of the aubergine right on top of the flame. Every 20 secs or so, give it a turn using a pair of metal tongs.
Cook the aubergine for about 5 mins till the skin starts to blister and the flesh starts to sizzle. Pop on a plate. Leave to cool, then peel the charred skin off the aubergine. Put the flesh into a bowl. Roughly mash the flesh with a fork.
Trim and slice the spring onion. Dice the tomatoes, discarding the white cores. Peel and crush the garlic. Roughly chop the chervil leaves.
Heat 2 tsp olive oil in a heavy-bottomed pan. Add the spring onion. Sweat for 2 mins till soft. Drain and rinse the lentils. Add to the onion with 300 ml boiling water. Cover. Simmer for 5 mins till heated through.
Brush the slices of aubergine you saved in step 1 with 2 tsp olive oil. Heat your grill to high. Grill the aubergine slices for 5 mins, turning once, till golden on both sides.
Stir the crushed aubergine, diced tomato, garlic and miso into the lentils and simmer for 1 min. Season to taste.
Ladle the lentils into warm bowls. Nestle the grilled aubergine slices on top of them. Garnish with the chervil and serve.