Cook sausages according to package instructions. Reserve, keeping warm.
While the sausages are cooking, heat a large, heavy-bottomed pot over medium-high heat.
Add half the butter and the olive oil to the pan. Add onion, garlic, carrots, and fennel to the pot and sauté until just tender.
Add the thyme, tomatoes, crushed red pepper, and deglaze with the wine.
Reduce the wine by half, then add the lentils and stock.
Bring the lentils to a boil, then reduce to a simmer. Cover and allow to cook for about 40 minutes or until tender and the stock has been absorbed, stirring occasionally.
Add additional stock if the lentils begin to dry out before they are fully cooked.
When the lentils are done, stir in the remaining butter and the parsley.
Transfer the lentils to a large-rimmed platter or serving bowl. Slice the sausages and place them on top of the lentils.