Heat 1 tablespoon of the butter in a skillet over medium-high heat.
Sear the Canadian bacon until the edges crisp, about 5 minutes. Transfer to a plate.
Whisk 6 eggs with the ¼ teaspoon salt and ¼ teaspoon pepper.
Melt the remaining 1 tablespoon butter in the skillet over low heat.
Add the eggs and stir slowly with a spatula until barely set and still very soft, about 2 minutes.
Remove from the heat, stir in the crème fraîche, and spread onto a plate to cool completely. The eggs finish cooking in the oven, so they should look underdone.
Dust a work surface with the 1 tablespoon of flour. Roll the puff pastry into a 10-by-14-inch rectangle.
Spread with the Dijon mustard, leaving a ½-inch border.
Scatter the cooled eggs over the pastry, then top with the Canadian bacon, aged cheddar, and the 2 tablespoons of chives.
Starting from a long edge, roll the pastry tightly into a log.
Chill the log for 10 minutes so it slices cleanly, then cut it into 6 equal rounds with a sharp knife.
Arrange the rounds cut-side up on the prepared baking sheet, spacing them at least 2 inches apart.
Beat the remaining egg and brush the tops and sides of the rolls.
Bake for 22 to 25 minutes, until deep golden brown and puffed.
For the hollandaise, combine the shallot, white wine, and white wine vinegar in a small saucepan.
Simmer over medium heat until reduced to about 1 tablespoon, about 3 minutes.
Strain, discarding the shallot, and let cool slightly.
Whisk the egg yolks, lemon juice, and the shallot reduction in a heatproof bowl set over a pot of barely simmering water until pale and thickened, about 3 minutes. Remove from the heat.
Slowly drizzle in the warm melted butter, whisking constantly, until thick and glossy.
Whisk in the 1 tablespoon chives, cayenne, and ¼ teaspoon salt. Keep warm, loosely covered, for up to 20 minutes, whisking in a teaspoon of warm water if it tightens.
Spoon the hollandaise over the warm rolls.
Finish with the remaining 1 tablespoon chives and serve immediately.