I've made the garlic optional, as the truffle paste is very garlicky. It depends how strong you like your gravy sauces.

Combine all in a blender and whizz until as combined as it can get to. Mine ended up with some tiny black dots in the sauce, which gave it a little character.

Heat in a pan until thoroughly hot. If it's a little too strong, add a little cream to dilute it.

As truffles can be an acquired taste, serve in a dish on the side, so that diners can choose how much to use.