Using a toaster, toaster oven, or regular oven, toast the English muffins until crisp, golden brown, and sturdy. Set aside.
Heat a large nonstick skillet over medium-high heat and cook 4 slices of the Canadian bacon, flipping once, until heated through and browned in spots, about 1 minute per side. Transfer to a large plate and repeat with the remaining slices.
Make the hollandaise: Melt butter in a small pot over medium heat until it’s foamy but not yet beginning to brown, 3 to 4 minutes.Place egg yolks and the water in a blender. Start blending, and, working very slowly, add the hot, melted butter until it’s all incorporated. (If it starts to get too thick to blend, add 1/2 teaspoon of water.) Add lemon juice, mustard, and cayenne, though feel free to adjust the amounts to taste, and season with salt and pepper.
Assemble the Benedict: place two muffin halves on a warm plate and butter them generously. Top each with a slice of Canadian bacon, then a poached egg. Spoon hollandaise sauce over and sprinkle with chives, flaky sea salt, and black pepper. Repeat with the remaining ingredients.
Serve immediately with a small side of home fries or cup of fresh fruit.