1. Thaw muffins overnight. Toast muffins in toaster or 375°F convection oven for 5-7 minutes or until toasted.
2. Pan fry ham slices. Keep hot and set aside for service.
3. Sauté baby spinach in oil and season with salt and pepper. Keep hot and set aside for service.
4. Prepare hollandaise sauce. In a medium mixing bowl, whisk together egg yolks, lemon juice, Dijon mustard, and salt. Set aside.
5. Melt butter in a saucepan until very hot.
6. While whisking vigorously, slowly stream butter into egg mixture and a sauce forms. Keep hollandaise sauce warm for service.
7. Bring a pot of water to a boil to poach eggs. Reduce to a simmer. Crack eggs into a mixing bowl. Alternatively, crack eggs into a strainer then transfer to mixing bowl to remove excess egg whites.
8. Stir pot of water with a slotted spoon. Gently tip eggs into the water one at a time, stir gently until the egg begins to set. Repeat tipping remaining eggs into the water. Cook eggs while stirring occasionally until egg whites set and yolks are soft.
9. Build muffins by shingling ham, layering with cooked spinach, top with poached egg, and pour hollandaise sauce.