Sort the lentils, discarding any blemished ones. Rinse with cold water and drain.
In large saucepan, cook bacon oven medium heat until crisp; remove from pan to a paper towel. Add chopped onion, carrot and celery to the saucepan; cook over medium-low heat, stirring occasionally, for 10 minutes.
Add mushrooms and garlic; cook, stirring often, for 3 minutes.
Add the lentils to pan along with chicken stock, water, rosemary, thyme, salt, pepper, hot pepper flakes and bay leaf; bring to boil. Cover and reduce heat; simmer for about 45 minutes or until lentils are tender. Remove and discard bay leaf. Stir in parsley, lemon juice and reserved cooked bacon.