How to Make It
In a medium saucepan, bring the corn cobs and cream to a simmer. Remove from the heat, cover and let steep for 30 minutes; discard the corn cobs.
Meanwhile, in a large saucepan, cover the potatoes with water. Add the garlic and a large pinch of salt. Bring to a boil; cook over moderately high heat until the potatoes are tender, 20 minutes.
Meanwhile, melt 1 tablespoon of the butter in a medium skillet. Add the corn kernels and 2 tablespoons of water, cover and cook over moderate heat until tender, about 5 minutes. Uncover and cook the corn over moderate heat, without stirring, until browned on the bottom, about 4 minutes. Scrape the corn into a blender. Add the corn-infused cream and puree until smooth.
Drain the potatoes and garlic and return to the saucepan. Shake the potatoes over moderately high heat for 1 minute to dry them; remove from the heat and mash with a potato masher. Stir in the corn cream, sour cream and the remaining 2 tablespoons of butter. Season with salt and pepper and serve.