In a wide pot, melt the unsalted butter over medium low heat.
Once melted, add the onion, carrot, celeriac, and leek. Cook, stirring occasionally, until softened.
Sprinkle the flour over the vegetables, then stir to coat evenly.
Once evenly coated, slowly pour in the vegetable stock, while continuing to stir, then the wine.
Pour in the 1 cup (240 milliliters) cream, then add the bay leaves and peppercorns.
Bring the mixture to a low simmer and cook, stirring occasionally, for 20 minutes.
While the mixture is simmering, whisk the 1/3 cup (80 milliliters) heavy cream either with a whisk in a large bowl or in a stand mixer with a whisk attachment just until stiff peaks form. Transfer to a bowl and refrigerate until ready to serve.
Place the clarified butter in a large skillet over medium low heat.
Add the bread cubes and toast, stirring often, until golden on each side.
Remove from heat, then dust with cinnamon until evenly coated.
Pour the soup through a fine mesh sieve into a large bowl (preferably with a spout). Add salt, nutmeg, and sugar. Adjust seasonings as needed.
Transfer the soup between individual bowls, then top with dollops of the whipped cream, a few of the cinnamon bread cubes, and the chopped parsley.
Serve immediately.