Allow to rest for at least 10 minutes before carving.


  • 1 x 800g piece of fillet steak
  • 2 tblsp vegetable oil
  • 1 large Spanish onion, peeled and sliced
  • 2 tblsp butter
  • 1 tblsp flour
  • 200ml cream
  • 1 tblsp Dijon mustard
  • salt and pepper
  • 4 large flat cap mushrooms
  • 1 sprig of thyme, chopped
  • 1 bunch watercress, washed and trimmed
  • 1 clove garlic
  • 2 tblsp olive oil


  • Preheat the oven to 140 degrees. Heat a pan with the vegetable oil until smoking. Colour the fillet on all sides until brown and crispy, season, then place on a wire rack in the oven for 30 minutes. This will give you a medium (pink) steak.
  • Meanwhile, melt the butter and add the onions and thyme. Cook with a lid on for 20 minutes over a very low heat until soft and add the flour and cook for three minutes before adding the cream, followed by the mustard. Season and set aside.
  • Crush the garlic into the olive oil and drizzle over the upturned mushrooms. Season and bake in oven for 5 minutes or so at 180 degrees.
  • Remove the beef from the oven and allow to rest for at least 10 minutes before carving. Serve with the creamed onions, the mushrooms, watercress and potatoes of your choice.