Position your oven rack in the center of the oven, and preheat to 400°F Prepare the muffin pans by spraying the cups and their rims with nonstick cooking spray, or putting the paper cups inside. If using silicon muffin pans, spray as directed and place on a baking sheet.
Whisk the flour, sugar, cocoa powder, baking soda, and salt in a medium bowl until well blended. Set aside.
In a large bowl, lightly whisk the egg, then whisk in the buttermilk and melted butter until smooth. Whisk in the vanilla, vinegar, and red food coloring until the mixture is uniformly colored. Use a wooden spoon to stir in the flour mixture, just until moistened.
Fill the prepared pans three quarters full. Use additional greased muffin pans for any leftover batter. Bake for 27 minutes, or until the tops are browned and cracked an a toothpick inserted into the center of one comes out with a few moist crumbs attached.
Set the pan on a wire rack to cool for 10 minutes. (While the muffins are cooling, you can make the dip.) Gently rock each muffin back and forth to release it, then remove them from the pan and put on the rack to cool for an additional 5 minutes. You can then dip the tops of the muffins into the vanilla dip. If you are going to store or freeze the muffins, put into airtight containers or freezer bags once the dip has set up. These muffins will keep for up to 24 hours at room temperature or up to 1 month in the freezer.
THis is a simple icing for baked muffins. Don't spread it with a knife-just dip the tops of the muffins into this thin glaze until they are lightly coated. The topping will be soft when set.
Stir the water, corn syrup,and salt into a small saucepan until the salt dissolves. Place the pan over medium heat and bring to a simmer without stirring. Once it simmers, remove at once from the heat and stir in the vanilla extract. Stir in the sugar in 1/4 cup increments until the dip is smooth. Transfer to a medium bowl to cool slightly, about 5 minutes.
Dip the tops of the cooled baked muffins into the mixture and let the excess drip back into the bowl. If desired, and any topping remains, dip the muffins a second time for a thicker glaze. Set the muffins right side up on a plate, and allow the dip to set at room temperature for about 15 minutes.