Place the bacon in a medium saucepan over medium heat. Cook the bacon until crispy, about 7 to 8 minutes. Remove the bacon from the pan with a slotted spoon, drain, and reserve. Brown the sausages, cut side down in the hot grease until golden, 2 to 3 minutes per batch. Remove the sausages from the saucepan and set aside.
Add the onions, fennel, and carrots to the saucepan and cook, stirring occasionally, for 3 minutes. Add the garlic and bay leaf and saute until fragrant, about 30 seconds. Add the lentils and stir to coat in the fat, about 1 minute. Return the browned sausages to the pan, stir in the thyme, tomatoes, and chicken stock, and bring to a boil. Reduce to a gentle simmer and cook 50 to 55 minutes, or until the lentils are tender and have soaked up most of the liquid. Remove and discard the bay leaf and thyme sprigs.
Serve the lentils and sausage with mustard and crusty French bread.
Yield: 4 to 6 servings