300g Roscoff onions, peeled and quartered
½ tsp salt
300ml water (for the brine)
100g nasturtium buds
100ml water (for pickle liquid)
100ml white wine vinegar
1tbs caster (superfine) sugar
100g shallots, peeled and sliced
200ml dry white wine
125g fresh chucked rock oysters, juice reserved
150ml grapeseed oil
Oyster juice, to loosen sauce
150g butter, diced
150g banana shallots, peeled and finely sliced
Salt, to season
250g 60-day-aged beef rump, trimmed and diced
1tbs Dijon mustard
1tbs nasturtium caper juice
1tbs extra virgin olive oil
Handful nasturtium leaves
Salt and freshly ground black pepper, to season
Sour onions (prepare a month in advance)
Place the onions into a jar with a seal-tight lid. Mix the salt with the whey and pour over the onions. Seal the jar and place in a store cupboard, out of daylight, to ferment for one month. They are ready when the onion starts to break down and they are acidic.
Nasturtium capers (prepare a week in advance)
Add the salt to the brine water in a pan. Bring to the boil until the salt is dissolved, then cool. Take a third of the brine and soak the buds for 24 hours. Drain, wash with cold water and repeat this process over three days. On the third day prepare the pickle liquid by adding the remaining ingredients to a pan. Bring to the boil, dissolve the sugar, then pour the liquid over the buds. Leave for at least three days.
Oyster emulsion (prepare on the day)
Add the shallots to a pan, pour over the wine and place on a low-medium heat. Boil until the wine has evaporated, remove and chill. Add the shallot mix and oysters to a blender and blend until smooth. Gradually add the oil until the mix is mayonnaise consistency. Add a little oyster juice to loosen the mix. Keep refrigerated until plating.
Shallot crisps (prepare on the day)
Place the butter in a wide, flat-bottomed pan on a high heat. Stir until the butter starts to foam. Add the shallots and cook, stirring, until the shallots start to brown and the butter smells like roasted nuts. Remove the pan from the heat and strain the shallots through a sieve.
Spread the shallot crisps on a flat tray on kitchen paper and season lightly with salt. Keep in a warm, dry place.
Plating the beef
Add the beef to a mixing bowl along with the mustard. Season with salt, pepper and the nasturtium caper juice, and finish with olive oil.
Place a large spoon of the oyster emulsion in the centre of the plates and spread it over the base of the plates with the back of a spoon. Scatter over the tartare, followed by a generous spoon of the nasturtium capers.
Next add the sour onion, in slices, over the top.
Dress some nasturtium leaves in the beef mixing bowl, add to the plates and finish with shallot crisps.
Recipe from London: The Cookbook (reviewed here). Photography by Jemma Watts