Cut the top off of the head of garlic and place in a shallow dish in 2.5cm of water. Drizzle with 2 tablespoons olive oil, sprinkle with basil, cover and place on a baking tray. Halve and seed the pepper, drizzle with remaining 1 tablespoon olive oil and place on the baking tray.
Bake garlic and pepper in preheated oven until pepper is browned and garlic is soft, 20 to 40 minutes. Remove from oven and when cool enough to handle, remove skin from pepper and chop. Squeeze out garlic cloves and mash together in a bowl to form a paste.
While garlic and pepper are baking, combine lentils and chicken stock in a large pot over medium heat. Bring to the boil, then reduce heat and simmer 40 minutes, until lentils are just tender.
Stir garlic paste, pepper, carrots, onion, asparagus, peas into lentil mixture, adding more stock to thin if necessary. Season with sugar, marmalade, curry powder, saffron, salt and pepper. Simmer 30 minutes more, until vegetables are tender and flavours are well blended.