Preheat the oven to 300 degrees F.
In a medium bowl, mix together the yeast and the warm water. Allow the mixture to rest (and allow the yeast to dissolve) in a warm area of your kitchen, about 5 minutes.
In a large bowl, combine the flour and sugar. Set aside.
In a pot or saucepan over medium heat, heat the milk until it is warm. Do not simmer or boil. Remove the milk from the heat, add 3 tablespoons of the butter and pour into a bowl to cool it slightly before mixing with the other ingredients.
Stir the yeast and water mixture and gently whisk in the flour and sugar. Finish by whisking in the milk mixture. Cover the bowl with a layer of plastic wrap and set aside in a warm place to rest for about 1 hour. What to look for: After about 1 hour (maybe a little longer) the batter should increase in volume and be somewhat "bubbly" in appearance. Cover and refrigerate until the next morning.
Remove the batter from the refrigerator and allow it to come to room temperature for about 15 minutes. When ready, whisk in the eggs and salt.
Heat a large cast iron pan (or, if preferred, a griddle). Melt 1 tablespoon of the remaining butter. Spoon the batter. Cook each pancake for a couple of minutes until you see bubbles on the surface. Flip on the second side, cooking for another minute. When done, place them on a plate, keeping them covered with foil in the oven until you build up a batch.
If making smaller pancakes, leave room between each pancake for "spreading". Adjusting the batter: This batter tends to be a little runny. Make a few pancakes. If they are spreading too much or coming out too thin, feel free to whisk in an additional tablespoon or 2 of flour to thicken the batter. Batter too thick? Add another egg or a little milk and blend.