Step 1

Heat 2 Tbsp. extra-virgin olive oil in a large high-sided skillet or a medium heavy pot over medium-high. Cook 6–8 smoked Austrian or German sausages (1–1½ lb.) , turning often, until deeply browned on all sides, about 4 minutes. Transfer to a plate.

Step 2

Combine 1 large red or yellow onion, finely chopped , 3 celery stalks, finely chopped , 1 large carrot, peeled, finely chopped , 1 tsp. freshly ground pepper , and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt , and remaining 2 Tbsp. extra-virgin olive oil in same pan. Reduce heat to medium and cook, stirring often and scraping up any browned bits stuck to bottom of pan, until vegetables are softened, 6–8 minutes. Add 5 garlic cloves, thinly sliced , and cook, stirring, just until fragrant, about 1 minute.

Step 3

Add 2 cups low-sodium chicken or vegetable broth , 1½ cups apple cider , 1½ cups French green lentils, picked through, rinsed , ½ cup finely chopped parsley , 3 Tbsp. Dijon or whole grain mustard , and remaining ½ tsp.…