For chili:

Toast cumin seeds in heavy small skillet over medium heat until fragrant, stirring often, 4 to 5 minutes. Cool; grind finely in spice mill or in mortar with pestle.
Sauté bacon in large pot over medium-high heat until brown and crisp. Using slotted spoon, transfer bacon to large bowl. Sprinkle beef with salt and pepper. Working in 4 batches, sauté beef in drippings in pot until browned, about 5 minutes per batch. Transfer beef and most drippings to bowl with bacon. Add onion and garlic to pot. Sauté until onion begins to brown, about 5 minutes. Add 1/2 cup broth to pot. Bring to boil, scraping up browned bits. Return beef, bacon, and any accumulated juices to pot. Mix in ancho chile powder, Texas-style chili powder, mole paste, 2 teaspoons salt, vinegar, oregano, and cumin seeds. Add 3 cups broth; bring to boil. Reduce heat to very low and simmer gently uncovered until beef is very tender, stirring occasionally and adding more broth by 1/2 cupfuls if chili is dry, about 2 1/2 hours. Mix in masa by teaspoonfuls to thicken chili or add more broth by 1/4 cupfuls to thin. Season chili with salt, pepper, and cayenne, if desired. DO AHEAD: Can be made 3 days ahead. Cool 1 hour. Chill uncovered until cold, then cover and keep chilled. Rewarm over low heat.

For garnishes:

Set out garnishes as desired. Ladle chili into bowls and serve.

Warm, freshly cooked or drained canned black beans or pinto beans
Chopped white, red, or green onions
Grated cheddar cheese, Monterey Jack cheese, or queso fresco
Sliced fresh or pickled jalapeño chiles
Tortilla chips or oyster crackers