Slow Cooker Sirloin Beef Tips in Mushroom Gravy!

Name: Slow Cooker Sirloin Beef Tips in Mushroom Gravy!
Cuisine: American
Ingredients: 3 pounds high quality sirloin (cubed 1-1 1/2 inch in size); 2 cubes of salted butter; 4 tablespoon olive oil (divided); 1/2 lb sliced mushrooms; 1 teaspoon seasoning salt (divided); 1 teaspoon white pepper; 1 tablespoon black pepper; 2 cups beef broth; 2 teaspoons dark brown sugar; 2 tablespoons Worcestershire sauce; 2 tablespoons ketchup; 1 teaspoon dried thyme; 1 cup diced onion; 3 tablespoons water; 1 teaspoon Adobo (red top); 2 cloves of garlic (minced); 1 teaspoon parsley; 2 teaspoons gravy master; 2 tablespoons cornstarch