Preheat the oven to 375 degrees F (190 degrees C).
Set an ovenproof skillet over medium-high heat, add sausage and cook, crumbling with a wooden spoon, until browned, about 5 minutes.
Add white parts of the onions and cook 1 minute.
Sprinkle flour evenly over sausage and cook, stirring constantly for 2 minutes.
Add milk and cook, stirring constantly until well blended.
Bring mixture to a simmer and cook until thickened, about 5 minutes.
Stir in remaining green onions and hot sauce and turn off heat.
Separate 6 biscuits, or as many as needed, into 2 or 3 layers and shingle biscuit dough over sausage mixture.
Brush a thin layer of egg evenly over biscuits and sprinkle evenly with everything seasoning.
Bake in the preheated oven until biscuits are golden brown and cooked through, 18 to 20 minutes.
