Bring a medium pot of boiling water to a boil over medium heat. Season the water with salt, then add the orzo and cook to al dente. Drain, reserving the cooking water.
In another pot of boiling water, over medium heat, blanch the leeks for 1 or 2 minutes, then remove and shock in a bowl of ice water. Drain and set aside.
In a skillet, over low heat, melt the butter and add the corn and scraped milk from all 4 cobs. Cook for 1 minute and add about 1 cup reserved pasta cooking water. Bring to a simmer and cook until thick and reduced, about 10 minutes, stirring occasionally. Add more pasta cooking water if gets too dry. Add the blanched leeks and heat through, about 1 minute. Add the orzo and toss to combine. Season with salt, to taste. Transfer the corn and orzo to a serving bowl, garnish with parsley and serve immediately.