Christina's Lentil Sloppy Joes

1 1/2 c uncooked green lentils (or other color)
4 cups water
1 lb ground beef
1 medium yellow onion, diced small
2 cloves garlic, minced
3 tablespoons chili powder
2 teaspoons oregano
1 teaspoon salt
15 oz can tomato sauce
1/4 cup tomato paste
3 tablespoons brown sugar
1 tablespoon yellow mustard

1. Put the lentils in a small sauce pot and pour in 4 cups water. Cover and bring to a boil. Once boiling, lower heat and simmer for about 30 minutes, until lentils are soft. Drain and set aside.
2. About 10 minutes before the lentils are done boiling, set a large frying pan over medium heat. Saute the ground beef and onion for about 7 minutes, crumbling with a spatula as you cook, until the beef is no longer pink. Add the garlic and saute a minute more.  Add the cooked lentils, the chili powder, oregano and salt and mix. Add the tomato sauce and tomato paste. Cook for about 10 minutes.
3. Add the brown sugar and mustard and heat through. Turn the heat off and let sit for about 10 minutes, so that the flavors can blend. Serve on bulky rolls.