Chop onion and saute in half the butter till softened. Do not brown.
Whisk in flour, then milk, and continue cooking till the sauce is thickened.
Add mashed carrots and stir to combine.
Transfer to a buttered [or spray with Pam] 9x13 baking dish. [Can use a smaller, square or round dish to reduce the quantity of topping]
Make topping: crush cracker and mix with remaining butter, melted.
Sprinkle topping on carrots. [Though the topping adds flavor, the carrot portion is very tasty on its own, so topping may be eliminated altogether.]
Bake in preheated 350°F oven for 20-30 minutes. [If casserole is prepared in advance and refrigerated, increase baking time at least 10 minutes.]
Note: One reader, Liza McCorkle, wrote to say that she really
likes this recipe, but when she added nutmeg and cardamom,it was significantly
better. Give it a try!