Pepper and Parmesan Popovers

I modified this from the Joy of Cooking popover recipe. Makes 6 popovers because that's how big my muffin tin is.

0. Preheat oven to 450 F. Put the muffin tin in there to warm up.
1. Whisk together 1/2 cup flour, 1/4 tsp salt, and 1/4 tsp pepper.
2. In another bowl, whisk together 1 egg, 1/2 cup slightly warm milk, and 1 tbsp melted butter.
3. Add the contents of the second bowl to the contents of the first bowl and fold together until just combined but still a tiny bit lumpy. Stick the bowl in the fridge for a few minutes.
4. Grate about 1/8 cup parmesan cheese and divide into 6 tiny little piles.
5. Pull the muffin tin out of the oven and quickly grease each cup. Pour 1/12 of the mixture (very approximately) into each cup, then throw a little pile of parmesan cheese into each one, then cover with more batter.
6. Bake at 450 for 15 minutes and at 350 for 20 minutes.

For some reason my popovers tend to turn out non-puffed and with a little pathetic hole in the bottom rather than a great glorious cavity in the center. I'm wondering if this is because cold batter doesn't interact well with a hot pan, though I read somewhere that cold batter + hot pan makes for poppier popovers. Maybe that was incorrect; maybe it's cold batter and pan + hot preheated oven, or something. It could also be that my muffin tin has pretty shallow cups and my popovers need big deep cups in which to maximize their potential. Maybe my popovers need a life coach.