Brush the sirloin steaks with the olive oil, season with salt and pepper and place the steak on the griddle pan. Cook each side for two minutes. Remove from the pan and allow to rest before serving.
Mix together the peas, broad beans, breakfast radishes and lettuce in a bowl. Mix in the potatoes.
For the tartare dressing, place the capers, gherkins, shallot, lemon zest and juice, garlic, thyme, chives and chervil in a bowl and mix with the rapeseed oil.
Put the oysters and their juice in a food processor with the mustard and blend until smooth. Gradually add the oil, blending as you go, until you achieve a mayonnaise consistency. Store in the fridge until you're ready to serve.
Spoon a little bit of the dressing directly onto the steak. And then run the rest of the dressing through the salad. Place the steak on a serving plate, serve with the salad and tartare dressing and place the oyster mayonnaise next to it.