In a bowl, combine lukewarm milk, butter, salt, eggs and vanilla extract. Stir to mix well.

Add flour and yeast and stir to mix.

Cover with plastic wrap and leave at room temperature for 1 hour.

You can cook now or leave in the refrigerator overnight.  I left it in the refrigerator and you should see air bubbles from the batter fermenting.  After the fermentation process, the batter thickens quite a bit and it was closer to bread dough than batter.

Add remaining milk and stir well.

Heat a waffle iron and spray well with non stick spray.  Pour in 3/4 cup batter (I have an 8-inch round waffle iron) and cook until well done; about 5 minutes.

Repeat until all the batter is used.