Preheat 350°F. Line a 9x5 loaf pan.
Stir together sugar crust ingredients.
Whisk sugars, oil, butter, yogurt, milk, vanilla, and vinegar.
Add remaining loaf ingredients.
Mix just until combined.
Transfer to pan and smooth top.
Rest 5-8 min.
Top evenly with sugar crust.
Bake 45-55 min.
Cool completely.
Whisk until smooth and pourable.
Spoon over slightly warm loaf.
Let set before slicing.
Best after chilling overnight.
