Pinned this recipe from sugarspunrun.com. This recipe was super interesting and unlike other muffin recipes I have made before. Room temp eggs and buttermilk, specific time waiting between adding things, temp change after several minutes in the oven. It was fun to try and definitely gave me big, fluffy, pretty muffins. My son loves them! I think the buttermilk is a great, different flavor for chocolate chip muffins. These are a delight.
Don't expect the muffins to pass the toothpick test when they are done. Follow the instructions about the browned tops. A toothpick inserted still came out gooey, but after the muffins cooled, they definitely were actually properly ready.
Don't be shy about the amount of coarse sugar you put on top. I should have used double what I did. Oh, and I made regular-size muffins, not jumbo ones. I'm mostly feeding them to a 2-year-old, so I probably should even have gone mini! :)