Winter Warmer Cottage Pie | BOSH!

Ingredients

• 2 tbsp olive oil
• 1 tbsp dried Italian herbs
• 1 tbsp tomato purée
• 1 tbsp Marmite
• 1 tbsp red wine vinegar
• 1 red onion
• 2 garlic cloves
• 1 leek
• 1 celery stick
• 2 carrots
• 250g chestnut mushrooms
• 1 x 400g pre-cooked lentils - vacuum packed or tinned / puy or beluga
• 150g frozen peas
• Salt & pepper to taste