Preheat oven to 220°C (or 200°C fan bake). If you don’t have a large oven-proof fry-pan, set aside a large baking dish.
Prep onion, mushrooms, carrot and courgette. Set aside separately.
Heat oil in a large, oven-proof fry-pan on high heat. Cook onion and mushrooms for 4-5 minutes, until softened and browned. Add sugar, spices and carrot to pan and cook for about 30 seconds, stirring, until fragrant.
Add stock, canned tomatoes, lentils and salt to pan and bring to a simmer. Reduce heat to minimum and simmer for about 10-15 minutes, until sauce has reduced slightly and lentils have softened. Remove from heat and stir through sour cream. Transfer mixture to baking dish, if using.
Carefully separate lasagne sheets and cut into rectangles (roughly 10x5 cm). Gently fold individual pasta sheets through sauce, ensuring sheets are separated and not sticking together. Top with courgette ribbons, dollops of ricotta and pesto. Drizzle with olive oil and season with salt and pepper.
Bake lasagne for about 15 minutes, until golden on top and pasta is tender.
Serve lasagne topped with basil.