Chop onion and celery. Heat olive oil and butter, over medium heat in a large saucepan or stock pot. Add onion and celery and cook for 3 minutes until soft. Add chopped garlic and cook for another three minutes, stirring often. Add cumin seed and cook until fragrant (only a few minutes). Peel and cube potatoes, add to pot and stir. Season with salt and pepper. Add vegetable stock bring to boil and then reduce heat. Simmer until potatoes are just tender, add corn 2 cups corn kernels and heat for 5 minutes. Using immersion blender (or food processor) puree until fairly smooth. Add milk and reservied 1/4 corn kernels and heat through -- do not boil. Serve topped with fresh parsley. Excellent with fresh rye bread.