Preheat the oven to 375 degrees F. Grease 11 cups of a standard-size muffin tin with nonstick spray. (They may stick to paper liners.)
In a large bowl, whisk together the yogurt, eggs, butter, molasses, and vanilla. (Yogurt can be lumpy so try to whisk it smooth.)
In a separate medium bowl, whisk together the flour, brown sugar, baking soda, cinnamon, ground ginger, allspice, and salt.
Gently fold the flour mixture into the yogurt mixture.
Divide the mixture among the prepared muffin tin, using 1/4 cup batter in each. Sprinkle the tops with coarse or decorating sugar if desired.
Bake for 14-16 minutes, or until a cake tester inserted into the center comes out clean. Let cool in the pan for a minute, then run a knife around the edges and transfer muffins to a wire rack to cool.
Notes
Once cooled, store in an airtight container at room temperature for 3-5 days. You can also store them in the fridge if you'd like, though they do firm up a little when cold.
If you don't have molasses, you can swap in honey. They will taste less like gingerbread, though.
Serve at room temperature or slightly warm, plain or topped with butter or cream cheese.
Dairy-free: Use vegetable or coconut oil in place of the butter and 3/4 cup nondairy milk in place of the yogurt.
Gluten-free: Use at 1:1-style gluten-free flour blend such as the one from King Arthur Flour.
Egg-free: Omit the eggs. Add 1/2 cup milk and proceed with the recipe.