Step 1

Preheat oven to 425°F. Place potato pieces in a steamer basket in a large saucepan. Add water to saucepan to just below basket. Bring to boiling. Steam, covered, about 20 minutes or until tender. Transfer potatoes to a large bowl and mash. Add 1 cup of the milk. Season with salt and pepper. Mix well. Set aside.

Step 2

In a large skillet combine the next six ingredients (through Italian seasoning) and ¼ cup water. Cook over medium-low about 10 minutes or until vegetables are tender, stirring occasionally.

Step 3

Meanwhile, place oats in blender or food processor; process until you have a flour-like consistency. In a small bowl whisk oat flour into the remaining 1 cup milk. Stir flour mixture into skillet with vegetables. Stir in vinegar. Taste and adjust seasonings. Cook until mixture thickens, stirring occasionally.

Step 4

Transfer vegetable mixture to a 2-quart baking dish. Top with mashed potatoes, spreading evenly.

Step 5

Bake 20 minutes or until potatoes are lightly browned on top. Let cool 10 minutes before serving.