Place the 2.2 lb (1kg) chuck roast, 8 cups (2L) water, or enough to cover, 1 white onion, 1 bay leaf, ½ tsp black peppercorns, and 2 cloves in a large pot or Dutch oven. Bring to a boil, uncovered, at 212°F (100°C ), skimming off any foam that rises to the surface.
Reduce the heat to a gentle simmer and cook, covered, for about 3 hours, or until the beef is fork-tender.
Remove the beef from the stock and set it aside to cool slightly. Strain the stock and reserve it. Finely chop the beef into small pieces.
In a small bowl, sprinkle the 2 tbsp unflavored gelatin powder over the ¼ cup (60 mL) water (room temperature) and let it bloom for about 10 minutes.
In the meantime, melt the ½ cup (115g) unsalted butter in a large saucepan over medium heat. Add the ½ cup yellow onion and saute until the onions start to sweat and turn translucent.
Then add the 1 cup (120g) all-purpose flour and cook, stirring constantly, for 1 minute to form a roux.
Gradually whisk in 3 cups (700mL) reserved beef stock until smooth. Cook, stirring frequently, for about 2-5 minutes, or until the mixture has thickened considerably.
Add the chopped beef, 2 Tbsp finely chopped fresh flat leaf parsley, 1 Tbsp Dijon mustard, and ¼ tsp ground nutmeg. Stir until evenly combined. Taste the mixture at this point, and add salt and pepper to taste as desired.
Remove the beef mixture from the heat and allow the mixture to cool to 120–140°F (48–60°C), then stir in the bloomed gelatin until completely dissolved and evenly incorporated.
Transfer the filling to a shallow dish (I used a 9x9 pan) and press plastic wrap directly on the surface. Refrigerate for at least 4 to 6 hours, preferably overnight, until firm.
Once chilled completely, scoop portions of the chilled filling and roll it into balls weighing approximately 20-25g each (about 1 Tbsp in size)
Lay out three shallow bowls with 2 cups (240g) all-purpose flour, 6 eggs (whisked) and 3 cups (450g) fine plain breadcrumbs in their separate bowls.
Roll each ball in flour, dip in the beaten egg, and coat with breadcrumbs. Arrange the bitterballen on a tray and freeze for 30 minutes. Then remove the tray from the freezer and repeat the egg and breadcrumb coating once more to create a double-breaded crust (to save time you can omit the freezing step, but your breading will be a little thinner and less crunchy. In this case, simply bread a second time right away).
Arrange the breaded bitterballen on a tray and refrigerate for at least 2 hours.
Heat about 1½-2” of vegetable oil to 350°F (180°C) in a large pot.
Fry the bitterballen in small batches for about 3 minutes, or until deep golden brown and crisp.
Drain on a wire rack or paper towels and allow to cool for a few minutes before serving.
Serve warm with Dijon or yellow mustard and enjoy!