Cinnamon Sugar Popovers with Nutella

Recipe found here.

1 tablespoon unsalted butter plus extra for greasing the pan
2 large eggs room temp
1 cup all-purpose flour
pinch of salt
1 cup milk whole or 2%, slightly at room temp
1 teaspoon ground cinnamon
1/2 teaspoon pure vanilla extract
powdered sugar for dusting
melted Nutella

Preheat the oven to 450°F, and thoroughly grease your popover pan. Melt the tablespoon of butter in a microwave safe bowl and set it aside to cool slightly. Break the eggs into the same bowl and whisk gently. Then whisk in the flour, salt, milk, cinnamon and vanilla extract until blended; a few lumps are fine.
Fill the cups 2/3 full (3/4 full for large popovers), and bake at 450 degrees for 15 minutes. Then, reduce the oven temp to 350 degrees and bake for an additional 20 minutes. (Do not open the oven! Opening the oven door in the first 20 minutes can cause them to collapse.)
When they are brown and crusty, remove them from the oven, and make a small slit in their sides with a sharp knife. Dust with powdered sugar and drizzle on some melted Nutella and enjoy immediately.