To roast garlic, see this tutorial. I like to roast a few bulbs at once (like 4-5) to have for the week.
Pierce potatoes (I used 2 large) all over with a fork and place on a paper towel, setting in the microwave. Microwave for 5 minutes, then flip and cook for 5 minutes more. Remove, slice in half and let cool until you can scoop out the flesh.
In a large bowl, coarsely mash beans with a fork. Add in sweet potato and mash together, then add in spices, salt and pepper, minced garlic, egg, panko and flour. Mix together until combined, then place bowl in the fridge for 15-20 minutes. This helps form them into patties, but as a warning they are still somewhat messy.
While mixture is chilling, combine yogurt/sour cream with 2 bulbs (squeezed out) of roasted garlic cloves, maple syrup and a sprinkle of salt and pepper in a blender or food processor. Process until smooth then set aside until ready to use.
Heat a large skillet over medium heat and add 2 tablespoons olive oil. Remove mixture from fridge and form into 4 equal patties, then place in the skillet once hot. Since the mixture can be wet and messy, do not move until they are fully cooked and golden on one side! This takes about 5-6 minutes. Then, add more oil if needed (this really helps cook them) and flip burgers very gently. Cook for another 5-6 minutes. Toast buns if desired.