Heat oven to 375°. In ungreased 1-quart casserole, mix hot water, milk, 2 tablespoons butter and the mashed potato mix. Cover with plastic wrap, turning back one side to vent steam. Microwave on HIGH 2 to 4 minutes or until moistened.

Whip patotoes with fork until fluffy; stir in chives. Smooth top of potato mixture with rubber spatula.

Crush crackers. In small bowl, mix crushed crackers, cheese and 2 tablespoons melted butter; sprinkle over top of potatoes.

Bake 10 to 15 minutes or until potatoes are hot and topping is crisp.