Very lazy lasagne - The Batch Lady

Ingredients

• 1 cup Onion (frozen & pre-chopped)
• 500 g Minced beef
• 2 cups Grated carrot
• 2 cans Chopped tomatoes
• 1 packet Passata
• 2 tbsp Tomato puree
• 3 tsp Dried oregano
• 1 tsp Garlic (frozen & pre-chopped) or garlic puree
• 1 pinch Salt
• 1 pinch Pepper
• 50 g Butter
• 600 ml Milk
• 4 tbsp Plain flour
• 1 tsp Cumin
• 2 cups Frozen sliced mushrooms
• 1 packet Lasagne sheets (dry not fresh)