Bring a large pot of water to a boil and add 1/2 teaspoon salt.
For Breadfruit: Peel and core the breadfruit. Cut into quarters and parboil until tender when tested with a knife. Drain and and cut into 1 1/2-inch cubes. FOR CASSAVA: Peel cassava and parboil until tender when tested with a knife, about 15 to 25 minutes depending on thickness. Drain and cut cassava into 1/2-inch thick slices. Cassava may be somewhat crumbly. FOR POTATOES: Peel, parboil whole and cut into 1/2-inch thick slices. Transfer parboiled starchy vegetable to a large mixing bowl.
Preheat the oven to 325 degrees F.
Heat a large saute pan and melt 1 tablespoon of the butter. Add onion and garlic and saute until translucent, about 5 minutes. Add celery and red pepper, and saute 5 minutes more. Add to bowl containing breadfruit, cassava, or potato and combine.
In a medium saucepan, melt remaining 3 tablespoons butter. Whisk in flour to form a roux, and cook for 1 minute. Slowly whisk in the milk and season with remaining 1/2 teaspoon salt and red pepper flakes. Heat until slightly thickened and add 2 cups of grated cheddar. Pour over vegetable mixture and stir gently until mixed.
Transfer mixture to a buttered 2 1/2-quart casserole dish, sprinkle the top with the remaining 1 cup grated cheddar, and place in the center of the oven, on a sheet pan. Bake for 35 to 45 minutes, or until heated through and cheese bubbles.
*Breadfruit is hard to obtain in the States but makes this dish most authentic. Two alternatives: cassava (called yuca in parts of USA, or sweet cassava in Jamaica) is long and brown, like a giant carrot, and often is sold with a waxed skin that needs to be removed. It is not related to breadfruit but is a starchy tuber with many of the same properties. Potatoes are an acceptable substitute for either tropical starchy vegetable. About 25 percent of the breadfruit and cassava are lost in trimming, less for potatoes.
Recipe courtesy of Katy Keck, Windjammer Barefoot Cruises