Using 2 rimmed sheet pans, roast 2 chopped leeks, 1 large onion, 4 carrots and 5 Yukon Gold potatoes that have been tossed with olive oil, salt & pepper at 500 degrees for 30 minutes (or until browned). Add sliced kielbasa to the roasting vegetables 15 minutes into the cooking time.
1/2 cup sour cream
2 Tbsp Dijon mustard or Dijon country-style mustard
1 tbsp water
Serve roasted kielbasa, vegetables with the mustard sauce.