Place a 12 well, metal muffin tin in the oven and begin preheating it to 425° F (218° C). If there are any racks above the middle one, be sure to move them.
Add all of the ingredients except for the butter, the flour, milk, eggs, sugar, vanilla, and salt, to a food processor bowl or into a blender. Process or blend on high speed for about 1 minute.
Turn off the machine and leave the batter to rest for 10 minutes. The batter will be very thin.
When the oven has heated to temperature, slice the butter into 12 equal pieces and drop 1 piece into each well. It may not melt fully.
Give a quick pulse or two to the batter then pour about 1/3 cup into each well or divide evenly between the 12. Bake for 12-15 minutes, until the pancakes are golden brown on the edges and are quite puffy.
Serve immediately.
Notes
Do ahead: mix the batter up to 12 hours ahead of time and refrigerate. Blend for 1 minute before baking.Adapted from The Kitchn