Chicken, asparagus and pea casserole

Ingredients

• 2 tablespoons olive oil
• 1.2 kilograms chicken thigh fillets, cut into thirds (halved if small fillets)
• 2 medium (240g) carrots, sliced thinly
• 1 medium (150g) brown onion, chopped
• 2 cloves garlic, crushed
• 1/4 cup (35g) plain flour
• 3 cups (750ml) chicken stock, approximately
• 1 cup (120g) frozen baby peas
• 2 bunches (340g) asparagus, trimmed, cut into thirds