Gather all ingredients.

Whisk butter and oil together in a small bowl. Reserve 2 teaspoons of butter mixture for later. Heat remaining butter mixture on 1 side of a large nonstick skillet over medium-high heat.

Place hash browns on buttered side of skillet in a round shape about 5 inches wide. Cook, undisturbed, until browned and crisp around edges, about 5 minutes.

Flip hash browns, and cook, undisturbed, until other side is browned and crispy, 4 to 5 more minutes.

Meanwhile, add reserved butter mixture to other side of skillet; add onion. Cook, stirring often, for 2 minutes. Add ham to onion, and cook 2 minutes.

Add onions and ham to top of cooked hash browns. Top with cheese slice; turn off heat.