- 6 potatoes, thinly sliced
- 1 large onion, cut into matchstick-size pieces
- 1/4 teaspoon garlic powder
- 1/4 cup water
- 3 tablespoons butter
- 2 tablespoons all-purpose flour
- 1/2 cup milk, or more as needed
- 1/4 cup Dijon-mayonnaise blend (such as Hellman's®)
- Combine potatoes and onion in a microwave-safe bowl. Sprinkle garlic powder over mixture and add water. Cover bowl and heat in microwave on high until potatoes are tender, 8 to 10 minutes.
- Combine butter and flour in a saucepan over medium heat; cook, stirring constantly, until butter is melted, 2 to 3 minutes. Slowly add milk and cook, stirring constantly, until mixture is the consistency of gravy, 2 to 3 minutes. Reduce heat; stir in Dijon-mayonnaise blend and mix well. Remove from heat and cover.
- Drain water from potatoes and pour gravy mixture over potatoes; stir to coat. Cover bowl and microwave on medium until flavors combine, 3 to 5 minutes. Let stand for 5 minutes before serving.