Lennies Chili Finally Written Down

Name: Lennie's Chili, Finally Written Down
Ingredients: 1 tablespoon olive oil; 1 1⁄2 cups chopped onions; 6 cloves garlic, minced (you can use less, of course); 8 mushrooms, thickly sliced; 2 lbs lean ground beef; 5 tablespoons chili powder, divided; 2 (28 ounce) cans plum tomatoes, drained; 2 (19 ounce) cans kidney beans, rinsed and drained; 1 tablespoon brown sugar; 1 tablespoon all-purpose flour; 1 tablespoon cocoa; 1 (14 ounce) can tomato sauce; 1 (5 ounce) can tomato paste; 4 teaspoons oregano; 1 teaspoon cumin; 1 teaspoon salt; 1 teaspoon fresh ground black pepper