Melt butter and honey in a small saucepan over medium-low heat. Split the whole vanilla bean in half lengthwise. Scrape all the seeds from 1 vanilla bean and place into saucepan along with the vanilla bean. Stir to combine; let simmer until sauce has thickened, about 5 minutes then reduce heat to low.
Preheat indoor grill pan to medium heat on stovetop.
Place mascarpone cheese and honey into a medium bowl. Split the remaining 1/2 vanilla bean in half lengthwise, scrape all the seeds from the bean and place into bowl; discard the bean. Stir to combine and set aside.
Cut each peach in half and discard the pit. Dip peaches cut side down into the butter-honey sauce and in batches, place onto hot grill pan. Grill for 2 to 3 minutes, until peaches have nice grill marks.
Combine walnuts and sugar into a bowl. Place grilled peaches, onto serving plates, 2 per plate. Top each with a dollop of mascarpone cheese and sprinkle with walnut sugar. Remove the vanilla bean from honey sauce and drizzle a spoonful of warm sauce over peaches and plates. Serve warm.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.