Preheat oven to 450 degrees.
Wash sweet potatoes and make a few holes in each one with a fork.
Rub potatoes with olive oil.
Microwave for eight minutes on high. Transfer to the oven and bake for about 25-30 minutes, until tender.
While potatoes are baking, heat butter in a saucepan over medium heat until melted
. Add flour and stir. When mixture thickens, gradually add milk
Stir until a thick sauce forms. Remove from heat and add 3 oz. blue cheese, salt, cayenne pepper, and black pepper and stir.
When potatoes finish baking, slice lengthwise and squeeze toward the center to fluff up cooked potato
. Pour cheese sauce over the potatoes, then garnish with remaining 1 oz. blue cheese and chopped green onion.