1/4 cup kosher chicken fat, duck fat or extra-virgin olive oil
To make the caramelized onions, in a medium saucepan over medium, heat the oil. Add the onion and salt and cook, stirring occasionally, until soft and quite golden, 10 to 15 minutes. Remove the saucepan from the heat and set aside.
To make the sliders, in a large bowl, gently mix the ground beef and onion powder (be careful not to over-mix). Form the beef mixture into 8 equal 2-by-3/4-inch patties. Transfer to a plate and set aside. In a wide, shallow bowl, mix together the matzo meal, salt and pepper.
Dip each beef patty into the beaten eggs, turning to coat, then transfer to the dish with the matzo meal. Turn gently to thoroughly coat. Return the coated patties to the plate.
In a large skillet, preferably cast-iron, heat the fat over medium-high. Fry the coated patties in the hot fat, turning once, until crusty and golden-brown, 3 minutes per side for medium-rare or 5 minutes per side for well-done. Serve topped with caramelized onions.
— Jim Romanoff