STEP #2 Prepare Filling: In medium mixing bowl mash polenta and cream cheese togetehr. Add lemon juice, zest, pepper flakes, celery & cilantro. Salt & Pepper to taste but not much - pancetta is salty. Place an iron skillet (or heavy, oven safe pan) on stove over medium heat, singfilling. Place an oven rack 5-6 inches from broiler element. Broiler to low setting.