Peel the potatoes and cut them into smaller pieces.

Put the potatoes in a saucepan and pour water over until just covered.

Boil the potatoes for 12-15 minutes under a lid.

Prick the potatoes to check if they are tender and sufficiently cooked. They should drop when you dot them.

Pour the water from the potatoes into a small bowl. It may need to be used later.

Mash the potatoes with a fork or mashed potatoes.

Add fat and whisk in the bog with a whisk until the lumps are gone.

Add infant formula and whip it into the bog.

Add a little of the saved potato water if the bog is too thick. Or pour in a little more milk.

Check that the bog has the right eating temperature before giving it to the baby. If the bog has become too cold, you can heat it a little.

You can scrape the mash through a sieve if you want a creamy mash without lumps.