75 g (2.6 oz) unsalted butter
  75 g (2.6 oz) plain flour
  500 ml (17 fl oz) full cream (whole) milk
  50 ml (1.7 fl oz) double cream (heavy cream)

  150 g hot-smoked salmon, flaked
  40–60 g cream cheese
  2–3 tbsp very finely diced red onion (or shallot for a more delicate flavor)
  1 tbsp chopped chives
  1 tsp lemon zest
  ½ tsp Dijon mustard
  White pepper
  Pinch of cayenne
  Salt to taste