Shred the duck meat and set aside for Duck Sandwich, recipe follows or use in another dish, reserve 1 cup for soup garnish.
Put the chicken stock and duck bones in a large pot and bring to a boil. Reduce the stock to a simmer and skim the impurities. Allow the stock to simmer for 30 minutes.
Pour the olive oil in a large pot over medium-high heat. Add the onions and garlic and saute until tender. Add the bay leaf, celery, and carrot and saute for approximately 2 minutes, until the celery and carrots are slightly tender.
Strain the stock into a pot and bring up to a boil.
Add the lentils and reduce the heat to a simmer for 30 minutes. Season the lentil soup with salt and pepper and garnish with shredded duck meat, tomatoes and chives.
For the mango chutney:
Put the palm sugar, water and star anise in a medium saute pan over high heat and bring to a boil. Once the palm sugar has dissolved, add the lime juice. Reduce the mixture to a thick, syrup-like consistency.
Add the mango and chile flakes and season with salt, cook for 5 to 7 minutes, until the mango has become tender and the juices have reduced.
For the salted pickled onion:
Put the onions in a bowl, add the salt and toss. Allow the salted onions to sit for 10 minutes. Rinse the salted onions under cold water, drain, and lay over a dry towel. Once dry, return the onions to the bowl and add the red wine vinegar and toss to coat and pickle the onions.
For the duck sandwich:
Preheat the oven to 375 degrees F.
Put the duck meat and baguette on a tray, heat until the meat is warmed through and the baguette is lightly toasted.
Put the baguette on a cutting board, layer the shredded duck meat over the bottom of the baguette, followed by the mango chutney, salted pickled onion, chives, cilantro and mint. Season with salt and pepper, put the top of the baguette over top, cut into portions and serve.