For a milder batch, remove all of the white membranes inside the jalapeños, and for extra heat leave some of the membrane and a few seeds in place. Wear kitchen gloves when handling jalapeños to avoid irritating your skin or eyes. These poppers can be assembled up to 2 days in advance and baked just before serving, or frozen unbaked on a tray and then transferred to a freezer bag for up to 1 month, adding a few extra minutes to the bake time if cooking from frozen.