Corn Chowder with Kielbasa

1 tablespoon butter
1 tablespoon olive oil
1 medium onion chopped, about 1 cup
2 tablespoons flour
2 cups chicken broth
2 cups milk
3 potatoes, peeled (or partially), chopped, about 3 cups
2 tablespoons chopped celery leaves
1 tablespoon dried parsley
1/2 teaspoon salt
1/2 teaspoon white pepper
3 cups corn, thawed if frozen
1/2 pound kielbasa (about 12"), halved lengthwise and cut in 1/2 inch slices

Heat olive oil and butter in large saucepan or Dutch oven and saute onions till clear. Stir in flour till it fully coats the onions and starts to brown slightly. Add potatoes, broth, milk, celery leaves, parsley, salt and pepper, stirring. Increase heat and bring to a boil, cover and simmer for 15 minutes, stirring once. Remove lid, adding corn and kielbasa, simmering another 10 minutes till potatoes are tender to fork. Serves 4.