Heat the oil in a large nonstick skillet over medium-high heat. Add the sausage and cook, breaking it up with a wooden spoon, until browned and cooked through, about 5 minutes.
Add the scallion whites, garlic, allspice, 1/4 teaspoon salt and 1/4 teaspoon pepper; stir for 30 seconds. Add the flour and stir until toasted, about 1 minute. Pour in the milk and chicken broth and simmer, stirring, until thick, 4 to 5 minutes. Stir in the scallion greens and parsley. Cover and keep warm over low heat.
Preheat a waffle iron to medium-high heat. Place 1 biscuit round into each section of your waffle iron, close gently (don't push down) and cook until golden and cooked through, 3 to 4 minutes. Repeat with the remaining biscuits.
Place 2 biscuits on each plate and top with the sausage gravy.