Heat vegetable oil in a skillet over medium-high heat and add sausage. Cook and stir, breaking up chunks with a spatula, until browned and crumbly.

Reduce heat to medium, add onions and a pinch of salt, and cook, stirring, until onions start to turn soft and translucent.

Stir in butter, and once melted, add flour. Cook, stirring, for about 2 minutes. Add diced apple, and cook, stirring for another minute or so.

Pour in chicken broth, raise heat to high, and stir, scraping up all browned bits. Add milk and bring mixture to a simmer. Reduce heat and simmer for 15 minutes.

Combine egg, cider, creme fraiche, thyme, 2 tablespoons green onions, salt, and baking powder in a bowl and whisk thoroughly. Add flour and mix until combined.

Taste gravy for seasoning and adjust with more salt, pepper, cayenne, green onions, and vinegar. Bring to a gentle simmer.

Transfer rounded teaspoons of dumpling batter on top of the simmering gravy. Cover and cook, untouched, for 5-6 minutes until dumplings are puffed up and cooked through.