Pre-heat oven to 350°F.
Spray an 8-inch square baking dish with cooking spray.
In a large Dutch oven, over medium-high heat, bring carrots and water to a boil.
Cook until just tender; 6 to 8 minutes; drain well.
In a large skillet, over medium heat, melt butter; add onion and garlic; cook until softened; about 6 minutes.
Stir in flour; cook, stirring constantly, for 2 minutes.
Stir in milk; cook, stirring occasionally, until thickened.
Remove from heat; stir in Cheddar, salt, and pepper until melted.
Add carrots; stir until well combined.
Pour mixture into prepared pan.
In a small bowl, stir together crackers, Parmesan and melted butter; sprinkle on top of the casserole.
Place in pre-heated oven and bake until hot and bubbly; about 30 minutes.
Remove from the oven and let stand for 10 minutes before serving.
