In a large saucepan or wok, heat oil on medium until oil begins to shimmer.
Add leek, carrots, celery and salt. Sauté 4-5 minutes. Add garlic and sauté 1-2 minutes.
Increase heat to medium-high and add ½ cup wine. Allow wine to cook down for 1-2 minutes, then lower heat to medium.
Add lentils, bay leaves and 2 cups water. Bring to a boil, and simmer about 25 minutes until most of the water has cooked down.
Add remaining wine and the mustard. Stir, and then simmer 5 more minutes.
Serve warm as a side dish, or with a chunk of crusty bread as a main course.
Leftovers:Store leftovers in the fridge, and use within 3-4 days.Make Ahead and Freeze:Let lentils cool to room temperature, and freeze for up to 6 months.
Notes
Recipe variations:
Substitute regular green orbrown lentils for beluga lentils. Reduce cook time by about 5 minutes.
Substitute French green lentils. Cook time will remain the same.