Perfect Popovers

1 3/4 cups whole milk
2 cups bread flour
3/4 teaspoon salt
1/2 teaspoon baking powder
3 large eggs, room temperature
2 tablespoons melted unsalted butter
1 tablespoon Dijon mustard

Note:  The key to making great popovers is having the eggs and milk at room temperature or warm before mixing.  It is also important to let the batter sir for an hour before baking it.  Popovers do not freeze well and pre-made batter has a tendency not to work properly the next day.

Place the milk in a bowl and microwave on high for approximately 1 1/2 minutes, or until warm to the touch.  Spoon the flour into a cup and level it off with a knife.  In a large bowl, sift the flour, salt, and baking powder together.  

In a blender combine the eggs, milk, melted butter and Dijon mustard; process approximately 10 seconds until blended.

Add flour mixture to egg mixture in blender.  Process approximately 10 to15 seconds or until just combined. Let rest for an hour if you can.

Preheat oven to 450 degrees F.  Place oven rack on the middle rung and heat an empty popover pan for 5 minutes, or until it is hot.  Once oven is the correct temperature and the empty popover pan is hot, quickly remove the popover pan from the oven; lightly spray the popover cups with a nonstick spray.

Fill the popover cups a little over 1/2 full.  Immediately place the pan back into the oven.

Bake without opening the door for 15 minutes. (A little less for mini popover pans).  Reduce heat to 375 degrees F. and bake for another 20 minutes or until deep golden brown on the outside and airy on the inside.

Remove popovers from the oven and unmold onto a rack.  Pierce the sides with the tip of a sharp knife to let steam escape and serve immediately with lots of butter.