In a heavy bottomed soup pot or 6-quart Dutch oven – warm the oil over medium-high heat then add the onion with the rosemary and a pinch of salt. Cook, stirring frequently until the onion begins to turn translucent about 5 minutes. Add the potatoes and cook until they begin to soften about 3 minutes. Then add corn, broth, and chili flakes.
Simmer the soup over medium heat for 20 minutes. Adjust the heat if needed to keep the soup from boiling.
Remove 2 cups of soup and puree in a blender (or with an emersion blender) until smooth, return the puree to the pot. Stir in the ham cubes and half n' half then simmer gently over low heat until the ham has heated through - about 5 minutes. Do not let the soup boil or the half n’ half will break and become lumpy.