Put the oil and the garlic in a small flat-bottomed saucepan. Heat over a medium heat.

When the garlic starts to go deep brown (15 - 20ish minutes) remove from the heat and allow to cool.

When cool strain the oil through a fine sieve into a sterilised jar. Here’s how to sterilise a jar.

The oil you make this way will keep for about a week in the fridge.

Feel free to combine garlic and onion if that’s what you want. I find it gives more flexibility to do them separately, but it is more of a pain to do.