Baked Potato and Carrot Mash

2 1/2 lbs potatoes , peeled and grated 1 cup onion , peeled and grated 1/2 cup carrot , peeled and grated 1/4 cup matzo meal 1 1/2 teaspoons salt 1/4 teaspoon[...]

1 lb carrot , peeled, halved lengthwise (if large, cut crosswise into 1-inch pieces) 1/3 cup water 6 tablespoons butter , room temperature, divided 3 large[...]