Melt the butter over medium-high heat. Add scallops in a skillet on a single layer and cook, flipping once until golden brown and translucent in the center. Set aside and keep warm.
Heat sesame oil in a skillet or wok over medium-high heat. Add shrimp and cook, stirring occasionally, until pink, about 2-3 minutes; set aside.
Add garlic to the skillet and cook for 1-2 minutes.
Stir in pre-cooked rice according to the instructions on the package, XO sauce, and fish sauce, breaking up clumps with a wooden spatula as you go along and tossing it with oil. Cook, stirring constantly until heated through, about 2 minutes.
Adjust seasonings with salt and black pepper. Toss for 30 seconds and add then add in scallions, shrimp, and scallops.