Thinly slice the onion. Cut the potato and carrot into 1cm chunks. Cut the chicken into 2cm chunks. Crumble 1 stock cube* into a heatproof jug, add 180ml (¾ cup) boiling water and stir to dissolve.
Step 2 — Brown chicken
Heat 2 tsp olive oil in a medium deep frypan over medium-high heat. Cook the chicken, stirring occasionally, for 3-4 mins until browned. Remove from the pan. Heat 2 tsp olive oil in the pan over medium heat. Cook the onion, potato and carrot, stirring occasionally, for 5 mins or until golden. Stir in 1 tbs plain flour and cook for 1 min or until golden.
Step 3 — Simmer filling
Add the chicken, stock and 60ml (¼ cup) milk to the veggie mixture and bring to the boil. Reduce the heat to medium. Cover and cook, stirring occasionally, for 15 mins. Uncover and cook for a further 5 mins or until the veggies are tender and the sauce is slightly thickened. Remove the pan from the heat. Taste, then season with salt and pepper.
Step 4 — Make mushy peas
Meanwhile, preheat the grill to high. Bring a small saucepan of water to the boil. Add the peas and cook for 2 mins or until tender. Drain, then return to the pan. Add 20g butter, season with salt and pepper and coarsely mash the peas.
Step 5 — Grill and serve up
Spoon the chicken filling into a 1L (4 cup) ovenproof dish (see Make it yours). Top with the mushy peas and grill for 3-4 mins until bubbling. Divide among plates and enjoy!
Step 6 — Make it yours
Fancy individual servings instead of one large pie? Simply divide the filling among two 500ml (2 cup) ovenproof dishes, then top with mushy peas before grilling.