Mix the dressing ingredients in a pan over a medium heat and bring to a gentle simmer. Cook for 8 minutes or until reduced to a thick, sticky mixture that thickly coats the back of a spoon.
Meanwhile, blanch the sugar snaps and green beans in a large pan of boiling water for 3 minutes, then drain thoroughly.
Toss onto a large platter with the lentils and red pepper, drizzle the sticky dressing over the top and carefully toss through with tongs. Scatter over the herbs and serve.