For the fennel: Heat a grill or grill pan over medium-high heat.
Slice a thin layer off the root end of each fennel bulb. Cut each fennel bulb into 8 wedges, keeping the root end intact. Chop 2 tablespoons fennel fronds and reserve. Bring a medium pot of salted water to a boil. Blanch the fennel wedges until crisp-tender, about 1 1/2 minutes. Remove from the water and set aside so the water evaporates and the fennel cools slightly.
Brush all sides of the fennel with the olive oil. Season with a sprinkle of salt and a grind or 2 of pepper. Place the fennel bulbs on the grill, 1 cut-side down. Grill the fennel until golden and caramelized, about 4 minutes. Flip and grill 4 minutes more on the other cut side.
Meanwhile, for the sauce: Brush the jalapeno with the olive oil and sprinkle with salt and pepper. Place the jalapeno on the grill and grill on all sides, turning while grilling, until some charring occurs, 10 to 15 minutes. Remove the jalapeno from the grill, remove the stem and chop the pepper very well. Place in a medium bowl with the honey, vinegar and reserved fennel fronds. Whisk to bring together and season with salt and pepper.
Remove the fennel from the grill and drizzle the sauce over the top. Serve warm.