Melt 2 tablespoons butter in a large saucepan. Add garlic and 1 tablespoon thyme; sauté 1 minute. Add broth, whipping cream, and 1 cup water. Bring to a boil; whisk in grits. Reduce heat to low; cook 10 minutes or until done, stirring occasionally. Season with salt and pepper. Keep warm.
Melt 2 tablespoons butter in a large skillet. Add celery and next 3 ingredients; sauté 30 seconds. Add shrimp, and cook 7 minutes. Remove shrimp from skillet. Add verjuice, and cook 6 minutes over medium heat or until most liquid has evaporated, stirring to loosen browned bits.
Reduce heat to low; whisk in remaining butter, 1 tablespoon at a time. Stir in lemon juice, tomato, and parsley. Serve over grits. Garnish, if desired.
*Verjuice is an acidic, sour liquid made from grapes. It's used like lemon juice or wine to heighten flavor.