Add the warm water to a large bowl and then sprinkle the yeast over the top as evenly as you can. Let stand for a few minutes, until the yeast granules dissolve. ½

Meanwhile, in a saucepan over medium heat, warm the milk until it's lukewarm, about "as warm as a baby's bottle". Remove from heat and stir in the melted butter. With your finger, test to make sure the mixture is lukewarm. If it's too hot, let it sit until it cools a bit (if it's too hot, it will kill the yeast).

Stir milk/butter mixture into the dissolved yeast mixture. Then add the flour, sugar, and salt, and stir until combined. It will not be completely smooth - small lumps are just fine.

Cover bowl with plastic wrap and let stand at room temperature overnight. The batter will bubble and rise, increasing in size.

The following morning, with a large whisk, beat the eggs, vanilla, and baking soda into the batter until completely combined.

Preheat waffle iron to desired temperature - my family prefers a medium-high setting. When the waffle maker shows "ready", let it heat for 2 more minutes. Lightly brush the waffle plates with melted butter or give the plates a quick spritz of non-stick spray, then close the waffle maker for a few seconds to heat up again. Pour batter onto hot waffle plates - for our 8" round waffles, we use a scant 3/4 cup of batter per waffle. Then shut the waffle maker lid (some batter will probably spill out) and let the waffle bake. You should see steam coming out of the waffle maker - let the waffle maker do its magic, no peeking! Our family has various preferences for doneness, so I bake the waffles between 3 and 4 minutes, depending on the person.