Gently pat chuck roast dry and season generously with salt and pepper.
Heat a large skillet over medium high heat and add 2 tablespoons olive oil to the pan. Add the chuck roast cubes to the skillet and cook each side for 3-4 minutes, or until lightly browned (no need to fully cook the meat, just brown the sides).
Transfer seared chuck roast to the slow cooker.
Tie the fresh thyme and rosemary bunches together using cooking string and place in the slow cooker on top of the chuck roast.
Return the skillet to medium high heat and add the remaining tablespoon of olive oil. Add the diced onion and sauté for 3-4 minutes, or until onion are translucent and starting to soften. Add the garlic and sauté for one more minute.
Transfer to the onions and garlic to the slow cooker.
For a final time, return the skillet to medium heat. Add the red wine and use a wood spoon to gently scrape off any brown bits that may have stuck to the pan. Whisk in the marsala wine, beef broth and tomato paste. Heat just until mixture is warmed through- no need to boil.
Add the chopped carrots, mushrooms, celery, canned tomatoes, and sun-dried tomatoes to the slow cooker and carefully pour the red wine mixture over the vegetables.
Cook on low for 6-8 hours or on high for 4-5 hours.
Approximately 15 minutes before serving, add the frozen pearl onions and stir in the cornstarch mixed with water (optional)*
Garnish with fresh chopped flat leaf parsley.