Fill a medium saucepan half full of water and bring to a boil. Add the pearl onions, cover, and set aside until onion skins are very soft and onions are easily peeled, about 10 minutes. Drain onions and refresh under cold running water or in an ice bath. When onions are cool enough to handle, use a paring knife peel away the tough outer skins. Set aside.

In a medium heavy pot render the bacon until crispy, 4 to 6 minutes. Remove bacon using a slotted spoon and transfer to paper towels to drain. Reserve and set aside.

Whisk the flour into the rendered bacon fat and cook, stirring constantly, for 2 to 3 minutes, until a blond roux is formed. Whisk in the chicken broth and cook, stirring, until mixture thickens. Add the heavy cream, thyme, salt, pepper, and Essence and cook until mixture is thick enough to coat the back of a spoon, 2 to 3 minutes. Add the pearl onions and continue to cook at a low simmer, partially covered, until onions are very tender and sauce is very thick and flavorful, 45 minutes to 1 hour. When ready to serve, garnish the onions with the reserved crispy bacon and sprinkle the top with the chives.