Ingredients
450-680g/1lb-1½lb of a chateaubriand
olive oil for brushing
ground black pepper
1 tbsp chopped fresh tarragon
Stage one ingredients:
1 small shallot, finely chopped
8 black peppercorns, lightly crushed
2 tbsp white wine vinegar
150ml/ ¼pt white wine

Stage two ingredients:
3 large egg yolks
1 tsp mustard powder
2 tbsp cold water
200g/7oz melted butter, preferably clarified, cooled

Method
1. Simply brush the steak with a little light olive oil and coarsely ground black pepper and then grill as desired - ideally it should be sealed on the outside and rare to medium in the middle. However you like your steak, this cut should not be overdone.
2. For the bearnaise sauce place all the stage one ingredients in a small pan and then reduce until about a quarter of its volume is left. Strain.
3. Now stage two - set a bowl over a pan of hot water over a low heat. Add the egg yolks, water and mustard into the bowl and whisk.
4. Pour in the vinegar reduction and whisk again over hot, but not boiling, water. Keep whisking until the sauce begins to emulsify.
5. Once at this stage add the melted butter a drop at a time and whisk in between each addition. The sauce will start to thicken.
6. Once all the butter is added, season and serve with the steak.