optional but recommended): In a large skillet over medium-high heat, sear the sausages for 2–3 minutes per side until nicely browned but not cooked through. This step builds deeper flavor and gives the finished dish that rich, dark look. If you’re short on time, you can skip this and add the sausages straight to the slow cooker.
Layer the onions in the slow cooker: Scatter the sliced onions evenly over the bottom of a 4- to 6-quart slow cooker. They form the bed that will soften, sweeten, and eventually become the base of your gravy.
Add the sausages: Nestle the sausages on top of the onions in a single layer if possible. They will sink down into the onions as everything cooks and softens.
Mix the simple gravy base: In a measuring cup or bowl, stir together the beef stock and
