Melt the butter.

Combine the milk, butter, eggs, Calvados, and salt in a large bowl.

Fold in the flour and sugar, being careful not to overwork the batter. The batter consistency should not be silky, but rather display small lumps. It should be somewhat heartier than Crêpe Suzette batter, but much thinner than pancake batter.

Heat a large skillet on medium.  Butter the skillet.

Deliver one ladleful of batter to the skillet, sloping and rotating skillet to spread the batter thinly and evenly.

When bubbles reach the surface, and the crêpe begins to lift from the skillet, flip the crêpe over for a few seconds.

Serve immediately, with butter and sugar or jam, or keep warm until serving.