Fill a small pot with an inch of water and bring to a simmer.

Melt the butter in the microwave.

In a stainless steel pan that can sit on top of the small pot, whisk together the egg yolks and lemon juice until thick and frothy.

Whisking constantly, place the pan on top of the pot; the water should not touch the bottom of the pan.

Continuing to whisk quickly so the eggs don't scramble, drizzle the melted butter into the pan. The sauce will thicken and double in volume.

Remove from heat and add cayenne and salt, continuing to whisk to eliminate any small lumps that formed.

Preheat oven to broil.

Fill a wide-bottomed pot with roughly two inches of water and bring to a simmer. Add white vinegar to help the egg whites set more quickly without spreading.

Stir quickly to swirl the water, then crack eggs in one at a time. Don't crowd the pot; work in batches if you're making a lot of eggs.

Keeping the water at a gentle simmer, cook 3 1/2 minutes for set whites and a soft yolk. Remove eggs individually with a slotted spoon.

Arrange canadian bacon in a single layer on a baking pan and broil for 2-3 minutes, keeping an eye on them until the edges are beginning to crisp. Flip and broil the other side for 1 minute, then remove.

Arrange english muffin halves in a single layer, cut side up, on the baking pan. Broil 1-2 minutes until toasted and remove.

Time to layer! Place the spinach (if using), canadian bacon, and poached egg on half of a toasted muffin and top with hollandaise sauce.