Heat the oven to 350 degrees F and arrange rack to lower middle of oven.
In saucepan, reduce jerk sauce to half and set aside.
In Dutch oven or other heavy-bottomed pot, melt 2T butter and oil over medium heat. Add onions and cook until golden and just caramelized. Set aside for later.
In same pot, melt remaining 8T butter. Stir in the flour and cook, stirring constantly, until the paste cooks and bubbles a bit, but don't let it brown — about 2 minutes.
Add 4c hot milk, continuing to stir as the sauce thickens. Bring it to a boil. Add salt and pepper, lower the heat, and cook, stirring for 2 to 3 minutes more.
Slowly begin adding cheese, constantly stirring and allowing cheese to melt and incorporate into sauce. As sauce begins to thicken, start to add additional milk alternating with cheese, then milk, etc.
Add reduced Mista Brown’s Original Jerk Sauce and stir.
Add cooked macaroni, onions and bacon to cheese sauce and gently mix together.
Place in large casserole or baking tin and cover with tight fitting lid or foil.
Bake for 20 minutes or until heated through.
Garnish with toasted garlicky bread crumbs, freshly grated parmesan, additional bacon crumbles, finely chopped chives and/or scallions. Serve with a salad as a main course or perfect for a decadent Thanksgiving side! (You can even prep the night before and refrigerate until the next day. Allow casserole to sit for at least 1 hour before placing in hot oven and allow for additional cooking time.)
*Pasta used is Melissa brand, imported from Greece and often used for Greek Lasagna (Pasticio). Substitute elbows, penne or your favorite sauce-soaking noodle.