Prepare the Fondant Sweet Potatoes:

1. Preheat oven to 375°F (190°C).
2. Sear the sweet potatoes: Heat butter and olive oil in a cast iron skillet (or an oven-safe skillet) over medium-high heat. Add the sweet potato rounds and sear for 3-4 minutes on each side until golden brown.
3. Add broth: Pour in the broth, and season with salt and pepper. Add fresh thyme sprigs (optional).
4. Roast: Transfer the skillet to the oven and roast for 25-30 minutes, flipping the sweet potatoes halfway through, until they are tender and have absorbed most of the broth.

2. Make the Maple Bourbon Pecan Glaze:

1. Simmer the bourbon: In a small saucepan, heat the bourbon over medium heat, letting it simmer for a couple minutes to reduce slightly.
2. Add syrup, butter, and sugar: Stir in the maple syrup, butter, and brown sugar. Allow it to cook together for 3-5 minutes until it starts to thicken.
3. Add pecans: Stir in the chopped pecans, vanilla extract, and a pinch of salt. Let the mixture simmer for an additional 2-3 minutes, allowing the pecans to get coated in the glaze.

3. Combine and Serve:

1. Drizzle the glaze: Remove the fondant sweet potatoes from the oven and drizzle the warm maple bourbon pecan glaze generously over the top.
2. Serve: Garnish with extra pecans or fresh thyme (if using) and serve warm.