Cajun Mushroom Slumgullion

Name: Cajun Mushroom Slumgullion
Ingredients: 2 tablespoons olive oil; 1 medium onion ; processed fine; 2 large carrots ; processed fine; 2 stalks celery ; processed fine; 1 teaspoon garlic ; crushed/minced; 8 ounces button mushrooms ; whole; 10 ounce can Rotel tomatoes with green chilis ; mild or regular, diced; 15 ounces tomato sauce; 6 ounces tomato paste; 1 pound lean ground beef; 1 tablespoon cracked black pepper; 1 tablespoon kosher or sea salt; 8 ounces elbow pasta; 1 tablespoon Cajun seasoning