Preheat the oven to 350 degrees F. Place the stuffing cubes in a large bowl and set aside. In a large sauté pan over medium-high heat, add 2 tablespoons butter and 2 tablespoons olive oil. Add the jalapenos, onion, bell pepper and thyme, then sprinkle with a pinch each of salt and pepper. Cook, stirring, until the onion and bell pepper are tender, then add the garlic. Cook until the garlic is tender, then remove the vegetables to the bowl with the stuffing cubes.
Wipe out the pan with a paper towel and place back on the heat. Add the remaining 4 tablespoons butter and 2 tablespoons olive oil to the pan. When the butter is melted and bubbling, add the plantains and sprinkle with salt. Saute, while tossing, until the plantains are golden and caramelized on the edges, 6 to 8 minutes. Pour over the stuffing in the bowl. Add the chicken stock and stir or mix with your hands.
Pour and press the stuffing into an 8-inch square baking dish, cover with foil and bake 30 minutes. Uncover and continue baking until golden, another 20 minutes.