Begin by filling a large skillet with water halfway up the sides. Add vinegar and bring to a low simmer.
While water is coming to a simmer, heat a large grill pan to medium hot. Spread butter on one side of each piece of bread. Grill bread and set aside to cool slightly. While bread is cooling, grill ham slices until heated through.
Break eggs into the water to poach. Remove with a slotted spoon when whites are cooked through but yolks are still runny (approximately 3 to 4 minutes) and place on paper towels to drain.
To assemble, spread grilled bread with orange marmalade. Top with 1 slice of grilled ham and one poached egg. Pour orange hollandaise over and garnish with orange zest.

Blender Hollandaise

Put egg yolks, orange juice, and salt in a blender and pulse to combine. Place butter in a microwave-safe bowl and microwave until melted. With blender running, gradually add melted butter into the egg mixture until smooth and frothy. Add a teaspoon of warm water if the sauce is too thick.