Preheat oven to 375 degrees F.
Bring a medium pot of water to boil and add in the sweet potato that has been peeled and cubed up. Boil sweet potato for 10-15 minutes, or until tender. Drain sweet potatoes and then mash well. You should have ~2-2.5 cups of sweet potato.
Next cook the elbow noodles according to the package.
While pasta is cooking, heat the olive oil in a large pan with onion and garlic. Cook for about 4-5 minutes over medium heat. Add the flour and whisk for 30 seconds and then slowly pour and whisk in the milk and vegetable broth. Bring to a boil and continue to whisk. Mixture should begin to thicken after 3-5 minutes. Place heat to low and mix in the mustard, salt, pepper, red pepper chili flakes, cheese and sweet potato. Stir well and then remove from heat.
Add in the noodles and mix in well. Taste and adjust any seasonings you may want extra. Pour in a oven safe casserole dish and top with panko crumb/Parmesan cheese mixture. Place in oven, uncovered, for 10-15 minutes, or until it gets bubbly.
Serve warm and enjoy!