Gardener's Pie

Ingredients

• 1 white onion
• 2 garlic cloves
• 4 carrots
• 1 bell pepper
• 1 cup frozen peas
• 1 tbsp tomato purée
• 1 tin lentils (400g)
• 1 tsp oregano
• 6 large potatoes
• 20 g butter
• 75 ml milk