Make the sauce: Whisk ingredients together. Refrigerate until needed.
Make the hollandaise: Using a double boiler, whisk egg yolks, water, and vinegar vigorously until the eggs turn cream-colored and are thickened, about 3 minutes. Remove bowl from heat and whisk in the lemon juice. Heat butter to 140ºF, then slowly add to the egg mixture while constantly whisking until all butter is incorporated. Add salt and pepper to taste. Set aside in warm area until needed.
To assemble: Spread 1 tbsp of sauce on the bottom half of English muffin. Layer lettuce, burger patty, caramelized onions, Canadian bacon, poached egg, a spoonful of hollandaise, and a sprinkle of chives. Top with the other half of English muffin.