In bowl, microwave potato and parsnips in 3/4 cup water, covered, until tender, 10 minutes; drain. Mash with butter and 1 tbsp. thyme; season. In cast-iron skillet, cook beef over medium-high, breaking up with a spoon, until browned, 8 minutes. Stir in remaining ingredients and 1/2 cup water; bring to boil. Season. Divide among ramekins; cover with potatoes. Bake at 475 degrees until golden, 5 minutes. Top with remaining thyme.