Chop off the stem and slice jalapeños down the center from top to bottom. Remove seeds and any white membranes you find, and discard. Soak jalapeños in a bowl of ice water for a hour as you prepare the other ingredients.
Grate your cheddar and chop the pecans and chives. Combine in a bowl with the bacon crumbles and mix in the mayonnaise.
Drain jalapeños and wipe off any extra water before filling each pepper with the bacon mixture. Serve immediately or chill until ready.