Mix the flour, salt, sugar and yeast in a bowl. Add the milk and eggs, knead for approx. 10 mins. using the dough hook on a food processor. Gradually add the butter and continue to knead for approx. 10 mins. Cover the dough and leave to rise for approx. 1 hr., then leave to rise in the fridge for approx. 8 hrs. or overnight. Divide the dough into 20 portions, shape into balls, flatten a little and place on a baking tray lined with baking paper. Cover and leave to rise for approx. 1 hr., brush with egg.
Approx. 20 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, leave to cool on a rack.
Slice the brioche buns crosswise, fill with cream cheese, cucumber, dill and salmon.