Preheat oven to 425 degrees.
Heat a Dutch oven or large deep skillet over medium high heat. Once the pan is hot, add the canola oil. When the oil is hot, add the onion, carrot and celery. Turn the heat down to medium and cook, stirring often for about 5 minutes or until vegetables are starting to soften. Add the garlic, give it a good stir and cook until garlic is fragrant, about 30 seconds.
Add the rosemary, thyme, bay leaf, smoked paprika, salt, lentils and chicken broth.
Bring to a boil, then reduce heat to low and simmer uncovered for about 30 minutes. During this cooking time you can start roasting the chicken sausages.
Once the liquid is mostly absorbed, stir in the Dijon mustard and red wine vinegar. Remove from heat and let stand for about 5 minutes.
In the meantime, Place chicken sausages on a baking sheet fitted with a wire rack. Spray the sausages with avocado oil (preferred) or cooking spray.
Roast the chicken sausages for about 20 minutes. Turn the sausages after 10 minutes of cooking. Cook until the sausage is golden and crispy.
To serve, scoop the lentils on a serving platter and top with the sliced sausages. Sprinkle with Parmesan cheese (optional), rosemary leaves or chopped flat leaf parsley for garnish.