1 Season each portion of beef then wrap tightly with the bacon.
2 Boil the potatoes with the stock and extra water to cover if needed. When the potatoes are soft, drain then mash with the olive oil. Season, cover and keep warm while heating the oven to 220C.
3 Heat a heavy-based frypan. Add 1 Tbs butter and 1 Tbs oil. When hot, add the bacon-wrapped beef, sear for 1 minute on all sides then cover and cook for eight minutes so it is medium.
4 Remove from the heat, cover with tinfoil and let rest.
5 To make the bearnaise sauce: Melt the butter. Place the vinegar and shallots into the saucepan and simmer until the liquid has reduced to 1 Tbs.
6 Pour this liquid into a small bowl, which needs to sit over a larger bowl of simmering water.