The texture of these sausage balls is a little less crumbly and more chewy than the classic recipe, plus they're packing extra protein! Make-ahead instructions in the recipe notes.
If you are baking these immediately, preheat the oven to 350℉. See notes for make-ahead instructions.
Mix all dry ingredients together in a large bowl or a stand mixer fitted with the paddle attachment (the baking mix, whey protein or powdered milk, and the dry seasoning.
After the dry ingredients are well combined, add the green onion, mix briefly, then the shredded cheese. Fold the cheese in gently to combine and coat with the dry ingredients so it doesn't clump up, either by hand or carefully pulsing the stand mixer a few times.
Mix the egg and buttermilk together in a large measuring cup. Whisk the egg lightly with a fork or small whisk. Set aside.
Crumble the sausage into the mixing bowl with the dry ingredients, and mix well. You can do this by hand but the mixture is stiff, so it's a lot easier with a stand mixer and paddle attachment! Once the sausage is starting to mix with the dry ingredients, add the liquid in the next step.
When the mixture is crumbly and beginning to come together, pour in the buttermilk and egg. Drizzle it in while the mixer is running if you can, or pour over the whole bowl if you're mixing by hand, rather than dumping it all in the center. You want to get everything well-incorporated, but stop after that. Overmixing can make the balls tough, or break up the cheese completely.
shape and bake sausage balls:
Form the mixture into evenly sized balls (a cookie scoop is the easiest way but you can do it by hand with a tablespoon). They will shrink a little bit in the oven but you want them evenly sized so they cook at the same rate, and no more than two-bites (no bigger than a golf-ball).
Bake on cookie sheets (lined with parchment for easier cleanup, if you like) in the 350℉ oven for 18-25 minutes, or until the center of the balls is 160℉ and the outsides are starting to brown.
Let cool slightly on wire racks or trays lined with paper towels. Serve immediately, or keep warm in a crock pot set to low/warm setting. Store any leftovers in the fridge or freezer, although these taste best when freshly baked.
Notes
To make ahead 1-3 days, keep everything cold while you work and store the balls in a single layer on a sheet pan (or multiple layers separated by parchment paper or plastic wrap if you're short on space- you may need to reshape them slightly before baking if they're stacked). To make ahead 3-6 months & have these on hand for company, freeze them unbaked in a single layer on sheet pans. Once they are frozen, package in airtight containers, freezer bags, or vacuum seal for 3-6 months (vacuum sealing may buy you extra time without risk of freezer burn). Bake from frozen and extend baking time (check temp in the center to make sure they're 160℉), or place on a sheet pan in the fridge to thaw at least 8 hours before baking.