Preheat your oven to 375°F (190°C). Grease a 12-cup muffin tin or line it with muffin liners.
In a skillet over medium heat, cook the ground sausage, breaking it apart with a spatula, until it’s fully cooked and browned. Drain any excess fat and set the sausage aside to cool slightly.
Mix Dry Ingredients:
In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, black pepper, garlic powder, and onion powder.
Combine Wet Ingredients:
In another bowl, whisk together the buttermilk, vegetable oil, and eggs until well combined.
Combine Wet and Dry Ingredients:
Add the wet ingredients to the dry ingredients, stirring gently just until combined. Be careful not to overmix, as this can result in tough muffins.
Add Sausage and Cheese:
Fold in the cooked sausage, shredded cheddar cheese, grated Parmesan cheese, and chopped chives or green onions if using. Mix until evenly distributed.
Fill Muffin Tins:
Divide the batter evenly among the prepared muffin cups, filling each cup about 3/4 full.
Bake:
Bake in the preheated oven for 20-25 minutes, or until the muffins are golden brown and a toothpick inserted into the center of a muffin comes out clean.
Cool and Serve:
Allow the muffins to cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely. Serve warm or at room temperature.