Preheat the oven to 350°F

Steam corn off for about 3 to 4 minutes. Strain and add to a small bowl; set aside

Wash the leeks well, making sure to remove all the grit and sand which is hidden between the leaves. On a cutting board, cut the leeks in half lengthwise, then slice them into half moons

Preheat a large skillet over medium heat; add the oil, leeks, and sauté until soft. Add the blanched corn and continue to cook for about 5 minutes allowing any water to evaporate; add the heavy cream, thicken with the slurry

Then add the Parmesan and mix well. Season with salt and pepper to taste. Transfer the mixture to an oven-proof casserole dish

Mix the Panko breadcrumbs, green onions, and parsley in a small bowl. Sprinkle the crumb mixture over the leeks and corn and bake in the preheated oven for 15 minutes

Remove from the oven, let stand for 5 minutes and serve