Chubby Hubby - One-pot wonder: vegetable lasagne

Ingredients

• 2 tbsp olive oil
• 1 onion, chopped
• 3 cloves garlic, minced
• 2 bell peppers, red/orange/yellow, de-seeded and cut into 1-cm dice
• 2 zucchinis (about 400g total), 1-cm dice
• 100g oyster mushrooms, cleaned and roughly torn
• 2 punnets shimeji mushrooms, snipped 1-inch from the base
• 1 x 14oz tin of tomatoes
• ½tsp sea salt
• ¼tsp black pepper
• 1 pack lasagne sheets (I used instant)
• 300g shredded mozzarella
• 250g ricotta cheese
• 1 egg