Heat half the oil in a large casserole and brown half the beef all over – about 3-4 mins. Remove with a slotted spoon and set aside. Repeat with the rest of the beef.
Add the remaining oil to the casserole and cook the onion for about 4-5 mins until beginning to soften. Increase the heat to high and stir in the carrots and chestnut mushrooms. Cook for a further 4-5 mins.
Return the meat to the casserole, add the flour, Dijon mustard and tomato purée and toss together well.
Pour in the stock and add the prunes, thyme and bay leaf. Bring to the boil then cover and simmer gently over a very low heat for 1½ hours until the beef is tender and the sauce is thick and glossy.
Meanwhile, place the chopped potatoes in a large saucepan and cover with cold water. Bring to the boil and simmer for 15-20 mins until very tender. Drain well and set aside. Return the empty pan to the hob and add the cream and butter. Heat gently until the butter has melted then return the well-drained potatoes to the pan and mash until smooth.
For toddlers, serve the stew and mash with some steamed green beans.
If you want to freeze some of the stew, leave it stew to cool completely then freeze in an airtight container for up to 3 months. Defrost completely (overnight in the fridge is best) before reheating in a saucepan until piping hot.
Cook's tip: this is a double recipe so you can freeze the second portion of stew for another time.