The perfect, unctuous sauce with steak, roast beef or pork.
1. Place a small saucepan over a medium heat. Add the butter and, without stirring, let it come up to what looks like a gentle 'simmer'. Skim off any white milk solids that float to the top; gently tilting the pan towards you can help this process. Some solids will sink to the bottom, but don't worry about these, you can discard them later in the process. Keep the butter in the pan so that it stays warm until you make the sauce, but don't be tempted to stir or agitate it as this will disturb the solids.
2. You'll need a heatproof, medium sized bowl that can sit stably over a medium saucepan. Half-fill the pan with water and bring to a gentle simmer - don't place the bowl over it yet. Add the egg yolks, lemon juice and dijon mustard to the bowl and stir well to combine.
3. Place 1-2 ice cubes and 1 tbsp cold water in a small bowl next to where you're working. Place the bowl containing the egg yolk mixture over the simmering water and cook for three minutes, stirring constantly so that the eggs don't scramble - add an ice cube if they start to turn. Bring the bowl away from the heat and place on to a damp tea towel to hold it still. The clarified butter should still be quite warm from the clarifying process; be careful to leave behind the remaining solids. Add the butter in a very thin drizzle, whisking constantly - you may need to pause every few seconds to ensure the butter is incorporated before adding more, otherwise the sauce may split.
4. When all of the butter is incorporated and you have a thick, glossy sauce, add the wholegrain mustard and a big pinch of a salt. Taste for seasoning, add a little more salt if you wish, and serve immediately.
2 egg yolks
1 tsp Dijon mustard
Juice of half a lemon
1 tsp wholegrain mustard