In a medium saucepan, prepare a white sauce
: melt the butter
, medium flame, and pour the flour
on it while stirring until well blended. On a more gentle flame, start pouring a bit of the cooking juice
and gently stir until it is incorporated ; keep doing this way until the white sauce
is ready (it must get thicker, but not too much ; reckon 10 minutes). The quantity of liquid you have might be slightly too much, don't hesitate to leave some away.