In a small heat-proof bowl, whisk together the Greek yogurt, egg yolk, lemon juice, Dijon mustard, sea salt, black pepper, and cayenne pepper until smooth.
Place the bowl over a small pot of simmering water (double boiler method) and whisk constantly for 3-5 minutes until the sauce is warm and slightly thickened, then remove from heat.
Fill a medium saucepan with water and the white vinegar, bringing it to a very gentle simmer.
Crack each of the 2 large eggs into a small ramekin, then gently slide them into the simmering water; poach for 3 minutes until the whites are opaque but the yolks remain soft.
While the eggs poach, split the English muffin and toast until golden brown.
In a dry skillet over medium-high heat, sear the Canadian bacon for 1 minute per side until warmed through and slightly browned.
Place two muffin halves on a plate, top each with two slices of Canadian bacon and one poached egg.
Generously spoon the warm hollandaise sauce over the eggs and garnish with freshly chopped chives.