Method

• 1.
  Place 1 tbs salt in a heap on a small tray. Press with the back of the spoon to make an indent to nest an egg yolk in. Crack a duck egg, separate the white (keep the whites, they make a great pavlova) and place the yolk in the salt. Gently spoon 2 tsp more salt over the top of the yolk. Repeat with remaining salt and second egg. Leave to cure in the salt for at least 1 hour (2 hours is ideal). Once eggs have been salted, gently pick them up and wash the salt off in a small bowl of water.
• 2.
  Place butter in a small frypan over medium heat and cook for 5-6 minutes until nutty and brown. Turn off the heat and leave to cool to room temperature. Place salted yolks in a jug and add vinegar and mustard. Gradually add the butter and use a stick blender to blend until thick and incorporated (like making a mayonnaise). Season. Set aside at room temperature for up to 2 hours.
• 3.
  Preheat oven to 200°C. Line a large baking tray with baking paper.
• 4.
  Combine oil and garlic in a small bowl. Arrange mushrooms, keeping any clusters together, in a single layer on 4 separate quadrants of the prepared tray (this is to create a ‘steak’ shape out of the mushrooms). Leave space around each group of mushrooms. Drizzle with garlic oil and top with thyme sprigs. Season generously with salt flakes and freshly ground black pepper. Top mushrooms with baking paper, then a second baking tray, squashing the mushrooms flat. Roast for 30 minutes or until mushrooms are tender and caramelised.
• 5.
  Increase oven to 220°C, remove the top baking tray and paper and cook for a further 10 minutes or until mushrooms are crispy. Serve mushroom ‘steaks’ with duck yolk sauce, watercress and lemon cheeks alongside.