Begin by filling a large skillet with water half 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 the whites are cooked through but the yolks are still runny (approximately 3-4 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 Orange Hollandaise: Put egg yolks, orange juice, and salt in a blender and pulse to combine. Place the butter in a microwave safe bowl and microwave until melted. With the blender running, gradually add the melted butter into the egg mixture until smooth and frothy. If the sauce is too thick add a teaspoon of warm water to loosen up.