Melt butter with milk, salt and 1/2 cup of water in a saucepan. Bring to a boil.

Add flour at once and, at medium low temperature, stir until mixture pulls away from the pan. Keep stirring over heat for 4 minutes to dry up the dough. The drier, the better.

Transfer dough into a mixer with a paddle attachment. Stir for a minute to cool off dough.

Add one egg, beat at medium speed for a minute, then add rest of eggs the same way. Add white and mustard and beat for a minute.

Slowly incorporate cheese and nuts.

On a cookie sheet lined with parchment paper distribute 1-tablespoon mounds of dough. Freeze. Once frozen, keep in an airtight plastic bag until ready to bake.

Bake on cookie sheet with parchment in preheated 375F oven for 29 minutes.