Butter a 9x13 inch baking dish. Scatter half the torn English muffins over the bottom, then half the Canadian bacon and half the cheddar.

Repeat with the remaining muffins, bacon and cheddar.

Whisk the eggs, milk, dry mustard, salt and pepper in a large bowl until no streaks of yolk remain.

Pour the egg mixture evenly over the muffins, pressing down gently with a spatula so the bread soaks it up.

Cover tightly and refrigerate at least 8 hours or overnight, so the bread fully absorbs the custard.

The next morning, preheat the oven to 350F and let the dish sit on the counter for 20 minutes while the oven heats.

Bake uncovered for 45 to 50 minutes, until the top is golden and the center only jiggles slightly when the pan is nudged.

Let rest 10 minutes; the center will firm up as it sits.

While it rests, blend the egg yolks, lemon juice, cayenne and salt in a blender for 10 seconds, then with the blender running, pour in the hot melted butter in a thin stream until the sauce thickens and turns pale yellow, about 1 minute.

Cut the casserole into squares, drizzle with hollandaise and scatter with chives.