Rub the serrano pepper with cooking oil and place on a foil-lined baking sheet. Cook under the broiler, turning over once, until blackened on both sides. Wrap the charred pepper in a paper towel and let it rest for 10 minutes. Using gloves, rinse under cold water and gently rub off the blackened skin. Remove the stem and seeds and dice.
In a large skillet, cook the bacon over medium heat until the fat has rendered and the bacon is crisp, about 8 minutes. Using a slotted spoon, remove the bacon and place on a paper toweled lined plate to drain. Remove all but 2 tablespoons of the bacon grease and discard. Paper towels work well for this.
Add the diced onion and celery to the skillet and cook over medium heat until softened, about 6 minutes. Sprinkle the flour over the onion and celery then add the corn kernels, diced potatoes, garlic and 1 cup of chicken stock and cook until the corn kernels are tender, about 12 minutes. Turn off the heat.
Reserve ½ cup of the cooked corn mixture. Using a ladle, carefully transfer the remaining corn mixture to a blender. Blend on high speed until smooth, about a minute.
Pour the puree into a large pot. Add the serrano pepper, remaining chicken stock, cumin, nutmeg, cayenne, cilantro, cooked bacon and reserved corn mixture. Stir to combine then bring to a boil. Reduce the heat and simmer for 10 minutes.
Reheating chowder with heavy cream over medium or medium high heat can cause it to separate. For the best result, only add cream to the portion of chowder that you are serving. If you are NOT serving the full batch, carefully ladle part of the chowder into another pot and set aside to cool and then refrigerate. Add a proportionate amount of heavy cream to the remaining chowder and stir. When ready to enjoy the leftovers, reheat the chowder over medium heat, then stir in the remaining cream and adjust the salt and pepper before serving.