Preheat your oven to 350°F (175°C). Prepare a standard muffin tin by either lightly greasing it with cooking spray or lining each cup with muffin liners to prevent sticking.
In a large mixing bowl, combine the all-purpose flour, granulated sugar, baking powder, baking soda, and salt. Whisk them together until they are well blended and free of lumps.
In another bowl, mix the buttermilk, egg, and melted unsalted butter. Whisk these wet ingredients together until they are smooth and uniform in consistency.
Gradually pour the wet mixture into the dry ingredients, stirring gently with a spatula or wooden spoon. Mix until just combined; it's perfectly fine if the batter remains slightly lumpy.
Carefully fold in the crumbled breakfast sausage, shredded sharp cheddar cheese, and finely chopped green onions.
Using a spoon or ice cream scoop, evenly distribute the batter into the prepared muffin tin, filling each cup approximately two-thirds full for optimal rising.
Bake in the preheated oven for 18-20 minutes. The muffins should turn a lovely golden brown, and a toothpick inserted in the center should come out clean when they’re ready.
Once baked, let the muffins cool in the tin for about 5 minutes. Then, transfer them to a wire rack to cool completely.
Notes
Serve warm with maple syrup or sour cream for added flavor.