Method

• 1.
  Place bone marrow in a bowl, cover with water and set aside overnight to remove any redness. Strain through a sieve, discarding liquid.
• 2.
  Place bread in a food processor and whiz until finely chopped. Transfer to a large, dry, deep frypan over medium heat and cook, stirring frequently, for 12-15 minutes or until golden. Set aside.
• 3.
  Clean pan and return to heat. Add 150g butter and cook until melted. Add bone marrow and cook, stirring constantly, until melted into butter.
• 4.
  Reduce heat to low. Add breadcrumbs and cook, stirring, for 2-3 minutes or until butter is absorbed. Add 1 cup (250ml) stock and cook, stirring, until stock is absorbed. Repeat, adding 1 cup at a time, until all stock is absorbed (this should take about 25 minutes).
• 5.
  Set aside for 10 minutes to cool slightly, then add mustard and orange juice. Working in batches, transfer to a blender and whiz until smooth.

• 6.
  Meanwhile, place oil and remaining 50g butter in a frypan over medium heat. Add mushroom and thyme, and cook, stirring occasionally, for 3-4 minutes or until golden.
• 7.
  To make the orange salt, combine orange zest and 1 tbs salt flakes in a bowl.
• 8.
  Divide soup between bowls. Season with pepper and serve topped with mushroom mixture, hazelnuts and a sprinkle of orange salt.