Preheat oven to 450°F and line a baking sheet with parchment paper or foil.
Put potatoes in a large pot and add water to cover. Bring to a boil then reduce heat and simmer for 25 minutes or until potatoes are tender when pierced with a fork. Potatoes should be cooked through but still hold their shape. Do not overcook. Drain potatoes and let cool for 10 minutes.
Place potatoes on baking sheet and gently press down on each with the palm of your hand until they split open and are about 1/2-inch thick but still in one piece. Space potatoes 1-inch apart. Brush with oil and flip to coat both sides. Sprinkle potatoes evenly with salt and pepper and cook for 20 minutes.
While potatoes are cooking, place garlic in the microwave and cook on HIGH for 30 seconds to soften and mellow flavor. Peel and place in a small blender or food processor with buffalo sauce and sugar; puree until smooth. Brush potatoes on both sides with mixture and cook for 5 to 10 minutes more or until potato edges are crispy and brown.
Stir together blue cheese yogurt dressing ingredients in a medium bowl and serve with potatoes.