Place all prepared ingredients in the slow cooker and cook on low for 6 to 8 hours or on high for 2 to 3. Before serving, taste for seasoning and add additional seasoning if desired. The sauce should be somewhat like a thin gravy, if it’s too thick add broth or water to thin if needed. Serve over white rice.
Heat a large sauce pan over medium to medium high heat. Add the butter to the pan, and next the cauliflower, shallots, and salt and pepper; cooking for 8 minutes. Add garlic, and cook an additional 1 minute. Sprinkle in the flour and stir into the veggies, it should look grainy, like wet sand. Slowly whisk in the broth a little at a time, stirring up the cooked bits on the bottom of the pan.
Brown the ground beef in a large skillet, and do not drain fat. Once the meat has browned add the onion and celery and cook until translucent and starting to soften. Add the flour, Worcestershire, and garlic powder, stirring to combine, cooking for 1-2 minutes.