Remove the outer leaves of the cauliflower, and wash if necessary. Trim ends, but leave the core intact. Set the cauliflower right side up on a cutting board and slice in 1/2 – 3/4 inch slabs. You should be able to get two large and two medium slabs, with a little left over on each side.
Season the slices with salt and pepper and thyme on both sides. Heat 1 tablespoon olive oil in a large skillet over medium high heat until it is shimmering. Add garlic and sauté for 1 minute. Add cauliflower and cook for about 2 minutes per side, until nice and golden.
Transfer to a baking sheet, brush with the remaining tablespoon of olive oil and roast for about 15 minutes, or until tender.