Peel the potatoes and grate them coarsely. Place in a clean tea towel and wring out as much moisture as possible before placing them in a bowl. Add half the melted butter, season and mix well. Heat a 20 cm (8 inch) non-stick frying pan, add the olive oil and the remainder of the melted butter. Put the grated potatoes into the frying pan and cook on a fairly high heat until the underside is browned. Remember to shake the pan so the potatoes do not stick. Next, turn the rösti over and continue to cook, shaking the pan occasionally, until the other side is browned. Place the rösti in the pre heated oven for 15-20 minutes, or until the potato is cooked right through. Remove from the oven and keep warm.
For the hollandaise sauce:
Place the egg yolks, salt and sugar in a food processor. Heat the wine vinegar, lemon juice and the white wine in a small saucepan and reduce by half. In another small saucepan melt the butter and allow to bubble, taking care not to burn it.
Set the food processor to high speed, and pour in the warm, reduced, wine vinegar liquid, followed by the hot melted butter, which should be added very slowly. That’s all there is to it: an easy classic hollandaise sauce which is great with everything from fresh asparagus to grilled fish.
For the asparagus and streaky bacon:
Pre heat the oven to 180C/350F/Gas 4
Lay the rashers of bacon on a baking tray and cook in the oven at the same time as the rösti until crisp. Remove from the oven, set aside and keep warm.
Cut the asparagus to about the length of your middle finger. Using a potato peeler lightly peel the bottom inch towards the cut end so you produce a white stalk and a plump green top. This all sounds a bit cheffy, I know, but think presentation, presentation. Reserve the trimmings to make an asparagus soup.
Blanch the asparagus in a saucepan of boiling salted water for 2 minutes. Drain immediately, and return to the same pan adding a generous knob of butter and seasoning to taste.
To serve, with a sharp knife, cut the warm rösti on a chopping board into 6 equal sized wedges, and place 1 in the centre of each serving plate. Lay a mound of asparagus on top of the rösti, spoon over the hollandaise and finally top with a strip of crisp, streaky bacon. Serve immediately.
Try to make this dish during the British Asparagus season. Asparagus growers generally say that the season lasts from end of April to end of June.