Place Infused Vinegar ingredients in a small saucepan over medium low heat.

Simmer for 2 minutes, then remove from stove and let it stand for 5 minutes to infuse.

Strain, pressing to extract as much liquid as possible. You should have around 1 tbsp of liquid. Cool 5 minutes before use.

Place butter in a jug and microwave until melted (1 - 1 1/2 minutes on high, but watch it carefully so it doesn't explode!).

Stand for 30 seconds until the milky whites settle at the bottom (this is the milk solids) and clarified butter (golden part) sits above it.

Pour off 175g / 3/4 cup of the clarified butter, discard the milky whites remaining. Use in this recipe while hot.

Alternative: Just melt 175g / 3/4 cup ghee, which is the same thing as clarified butter.

Place egg yolks, infused vinegar and salt in a tall, narrow container that the blender stick fits in all the way to the base. Blitz briefly to combine.

With the stick blender going on high, slowly drizzle the butter in over about a minute. Important: The butter must still be hot! If it has cooled, reheat until hot.

After all the butter is in, blitz for a further 10 seconds, moving the stick up and down.

Thickness: Add 1 tablespoon water, then blitz to incorporate. Add more water as needed, 1 teaspoon at a time, until the Bearnaise Sauce is a thick sauce but loose enough to ooze across a steak, coating it thickly.

Fresh herbs: Stir in tarragon and chervil.

Using: Use immediately, or keep warm until required. I use a thermos – a good one will keep it warm for at least 1 hour. Use warm or at room temperature. See note for storing and reheating.