In a little saucepan, quilt the lentils with 1 scramble of water and add a sizable pinch of salt. Duvet and carry to a boil. Simmer over low warmth, stirring infrequently, till unexcited, about 20 minutes. Drain.
In a sizable saucepan, prepare dinner the pancetta over reasonably low warmth, stirring, till rather a lot of the rotund has been rendered, about 8 minutes. Add the garlic, carrots, celery, onion, potato, celery root, squash, rutabaga and bay leaf and prepare dinner over reasonably excessive warmth for 2 minutes, stirring to coat with rotund. Season with salt and pepper and prepare dinner till the greens soften, about 3 minutes longer. Add the chicken inventory and carry to a boil. Cleave the warmth to low and simmer till the greens are unexcited, about 20 minutes. Discard the bay leaf.
High-tail within the lentils, parsley and thyme and season with salt and pepper. Ladle the soup into bowls, high with Gruyère shavings and wait on piping hot.
The soup can be refrigerated for 3 days.