Coat a 9-by-13-inch baking dish with cooking spray.
Heat oil in a large skillet over medium heat.
Add onion and cook, stirring, until starting to soften, about 3 minutes.
Photo: Jason Donnelly
Sprinkle flour over the onion and cook, stirring, for another minute.
Bring to a simmer and cook, stirring, until thickened, 3 to 4 minutes.
Remove from heat and stir in Cheddar, sour cream and Parmesan.
Fold in hash browns.
Transfer the mixture to the prepared baking dish and sprinkle with crushed potato chips.
Bake until golden and bubbling around the edges, 40 to 45 minutes.
Let rest for 10 minutes before serving.
- Daily Values (DVs) are the recommended amounts of nutrients to consume each day.
(-) Information is not currently available for this nutrient.
