With a sharp knife, cut a thin slice off the stem end of the fennel bulb and discard. Remove the stalks and fronds by cutting about 1-inch above the fennel bulb. Reserve fronds for garnishing at the end.
Cut the bulb in half lengthwise from top to stem end.
Using a medium bowl, whisk together the olive oil and honey. Add the fresh thyme sprigs and fennel and gently toss to coat.
Place the halves, cut-side down, on a parchment-lined baking sheet and season with salt and pepper.
Roast in a preheated 400°F oven for 225 minutes or until tender and browned.
To serve, place fennel cut-side up and drizzle with balsamic vinegar and garnish with reserved fronds.
