White Castle-Style Mini Burgers

Ingredients:

• 1 onion, finely chopped
• 280 g lean ground beef (20% fat)
• 1 tsp onion powder
• 1 tbsp (15 g) unsalted butter, cut into pieces
• 8 slider buns, cut horizontally in half
• 8 thin slices of pickled cucumbers

Preparation:

1. Place the onion in a bowl and cover with 0.5 cups of water. Let it sit for 30 minutes.
2. Meanwhile, in a food processor, pulse the ground beef with 2 teaspoons of water, onion powder, 3/4 teaspoon of salt, and a small amount of black pepper until smooth. On a sheet of parchment paper, draw a 12 x 6-inch rectangle; flip the paper over (you'll still see the rectangle).
3. Place the beef in the center of the outline; cover with another sheet of parchment and press down so the meat mixture completely fills the rectangle. Remove the top sheet and use a knife to mark 8 3-inch (7.5 cm) squares on the ground beef. Use a chopstick to poke 5 holes in each square patty (one in the center and one near each corner). Transfer them to a parchment-lined baking sheet, cover with plastic wrap, and freeze for 10-15 minutes.
4. Trim the edges of the rectangle to make it even; cut out the patties along the lines. Heat a very large skillet over medium-high heat. Add the onion and water; bring to a boil. Stir in the butter and arrange the patties on top of the onion. Cook until the meat is darkened around the edges, 3 to 4 minutes.
5. Place a bun, bottom side up, on top of each patty. To warm the tops of the buns, bridge them over the edges of two adjacent inverted buns. Continue cooking until the patties are cooked through, about 2 more minutes, adding 1-2 tablespoons of water if the pan is too dry or the onions are starting to burn.
6. Remove the bun tops from the pan. Insert a spatula under each patty, lifting them along with the onions and buns; invert onto a plate. Top each burger with a dill pickle slice and the top half of the bun.