Zucchini, pea and mushroom pastitsio

Ingredients

• 250 grams penne pasta
• 1 tablespoon oil
• 1 onion, finely chopped
• 2 cloves garlic, crushed
• 250 grams button mushrooms, sliced
• 2 zucchini, halved lengthways, thinly sliced
• 1 1/2 tablespoon cornflour
• 1 1/2 cup (375ml) milk
• 1/2 cup (60g) grated tasty cheese
• 1 cup (120g) frozen peas
• 1/2 cup (100g) ricotta, crumbled
• 1 bunch chives, snipped
• 1/4 cup (20g) grated parmesan