Preheat the oven to 375 degrees F. Melt 1 tablespoon butter in a skillet over medium-high heat. Add the shallot and cook until softened, about 1 minute. Add the corn and jalapeno; cook, stirring, until softened, about 3 minutes. Add the sherry and cook, stirring, until evaporated, about 2 minutes. Season with salt and pepper.
Transfer the corn mixture to a large bowl and add the crabmeat. Stir in the monterey jack, sour cream and 1/2 cup crushed crackers. Transfer to a 1-quart baking dish.
Combine the remaining 1/2 cup crushed crackers with the cheddar, chives and Old Bay in a medium bowl. Work the remaining 1 tablespoon butter into the crumb mixture with your fingers until combined. Sprinkle the crumb topping over the crab mixture. Bake until golden brown and heated through, about 20 minutes.