Preheat oven to 350°F (175°C).
Heat a large skillet over medium/medium-high heat.
Add the oil and once hot, stir in the garlic, being careful not to burn.
Add in the lamb and stir, combining with the garlic.
Cook until the meat is browned.
Remove the lamb/garlic mixture from the pan, then add in the onions, carrots, celery, rosemary, and thyme.
Cook until onions are translucent and carrots and celery softened.
Add the meat mixture back into the pan, and stir in the tomatoes, balsamic, and Worcestershire and bring to a simmer.
Pour meat/vegetable mixture into a 9 inch x 13 inch (23 cm x 33 cm) baking pan, and with a rubber spatula spread a layer of the Mashed Cauliflower over the top, forming a solid layer of the mash.
Bake for 20 minutes or until the mashed cauliflower is slightly browned on top.