Preheat the oven to 205°C (400°F).
On a parchment-lined baking sheet, toss the potato sticks with half of the rendered duck fat. Season with salt and pepper.
Bake for 45 minutes to 1 hour, stirring occasionally, until the fries are golden and crispy.
Meanwhile, heat the olive oil for the sauce in a saucepan over medium heat. Cook the onion for 1 minute.
Add the remaining sauce ingredients to the saucepan. Bring to a boil, then simmer for 15 to 18 minutes over medium-low heat. Remove from heat.
Using an immersion blender, blend the mixture until smooth.
In a large cast-iron skillet, heat the remaining duck fat over medium heat. Sauté the red onion for 2 to 3 minutes. Set aside in a bowl.
Spread the fries in the skillet. Top with the smoked duck meat and red onion. Drizzle desired amount of barbecue sauce and cover with cheese.
Continue cooking in the oven for 8 to 10 minutes.
Set the oven to broil and cook for an additional 2 minutes until the cheese has melted.
