Melt the butter in a saucepan over medium-high heat until it foams. Add the pecans and toss to coat evenly; toast for about 1 minute. Add the brown sugar and swirl until it melts; toss to coat the nuts. Add the bourbon and maple syrup and remove from the heat. Swirl the sauce to mix, and then allow to cool slightly in the pan. Pour the sauce over scoops of ice cream to serve as a sundae. Season with a little pinch of salt. Serve immediately.