Refrigerate cooled muffins within 2 hours because the centers contain cream cheese and egg yolk. Store them in a shallow airtight container for up to 5 days with parchment between layers. For freezing, wrap each muffin tightly and place them in a freezer bag for up to 2 months. Thaw overnight in the refrigerator so condensation doesn't soak the tops. Reheat one refrigerated muffin at 300°F for 7 to 9 minutes. A microwave works for 12 to 15 seconds, but it softens the pepitas. Let the muffin stand for 3 minutes before eating because the filling heats faster than the crumb. Discard muffins with a sour smell, wet sticky tops or any visible mold. When unsure, throw the muffin away rather than tasting it.