Once the mixture of flour and butter has sautéed a bit, gradually add the milk and vegetable stock while whisking. After it has been whisked in, add the white wine, lemon juice, finely grated lemon zest, salt, sugar, and pepper.
½ dl white wine, 2 ½ dl milk, 2 ½ dl vegetable stock, 1 lemon, ½ tsp sugar, 1 ½ tsp salt, Pepper