Use a dump paper towel to wipe each mushrooms, cut a thin slice off the bottom of each stem and give mushrooms a rough chop. Add them to a food processor and pulse for a few times until mushrooms resemble ground "meat".
Heat 1 tablespoon of olive oil in a medium non-stick skillet and over medium heat. Add ground mushrooms and cook stirring occasionally for 7-10 minutes or until liquid evaporates and mushrooms begin to brown.Transfer mushrooms to a separate plate.
To the same pan add the remaining 1 tablespoon of olive oil, onion, carrot, celery and ¼ teaspoon of salt and cook until onion is translucent, about 7 minutes. Add garlic and cook for 30 more seconds.
Add the cooked ingredients in your slow cooker along with the tomato paste, maple syrup, crushed tomatoes, Worcestershire sauce, liquid smoke, Italian seasoning, water and the remaining ½ teaspoon of salt and pepper.
Cover the lid and cook on low for 4 - 4 ½ hours or on high for 2 - 2 ½ hours. Adjust the seasoning and serve.