Step 1

Preheat oven to 350° F.

Step 2

Grease a 7x11 baking dish. Slice kielbasa into four even pieces. Slice down the middle of each piece so that the kielbasa will lay open flat. Place in baking dish and set aside.

Step 3

Peel and cut potatoes into even pieces. Place in a large pot, cover with water, and cook for 15 minutes, or until potatoes test done with a fork. Drain.

Step 4

Using a hand mixer, beat the drained potatoes until smooth. Add milk, beating again until smooth.

Step 5

Add the cheese, mustard, salt, pepper, and butter to the potatoes, again beating until smooth.

Step 6

Divide potatoes and place a mound on each of the four pieces of kielbasa. (Any extra potatoes can be baked in a small greased casserole or custard cup.)

Step 7

Bake for 20-25 minutes, or until kielbasa is hot and potatoes have lightly browned edges.

Step 8

Serve immediately.