• Pat the chuck roast dry with a paper towel. Season with salt and pepper. Heat the pan/skillet to medium-high. Add 2 tbsp butter, olive oil and wait for it to get hot. Sear the roast chunk for 4-5 minutes per-side. Remove the roast and set aside.
• Add 2 tbsp butter and wait for it to melt. Add sliced onions and sauté for 10-12 minutes or until caramelized. Add minced garlic and sauté for 1 minute.
• Place the seared roast in the slow cooker. Add cajun seasoning, caramelized onion, beef broth & bay leaves.
• Cook on low for 8-10 hours or high for 5-6 hours or until fork tender.
• Discard the bay leaves. Remove the roast and place in a medium-large sized bowl. Using 2 forks, shred the meat. Cover with aluminum foil until ready to eat. 
• In a small bowl: combine cornstarch and water, mix until the cornstarch is fully dissolved.
• Transfer the broth to a pan. Add cornstarch mixture and mix. Turn the heat to medium and let simmer for 10-15 minutes or until thickens to your liking. Season with salt & pepper to taste. Optional- Set the slow cooker to high. Add cornstarch mixture to the slow cooker and simmer for 20 minutes or until desired consistency. Season with salt & pepper to taste.
• Pour 1-2 cups of gravy over the shredded meat and mix.
• Toast Bread - Preheat the oven to 300°F (148°C). Slice the bread in half (vertically). Spread melted butter/ mayo on the inside of the bread. Lay the bread butterside down on a baking pan. Bake for 2-3 minutes. Remove bread from the oven.
• Prepare Sandwich - smear a generously amount of mayo on the bread. Add shredded meat, lettuce & tomatoes on top. Place some of the dip in a small serving bowl.

Serve immediately. Dip the sandwich in the gravy and enjoy!