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1
Preheat the oven to 450F.
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2
Drizzle 2 tablespoons of the olive oil into a 9 x 13-inch baking dish and use your hand to evenly coat the entire surface.
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3
Set aside.
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4
Heat the remaining 3 tablespoons olive oil in a large frying pan over medium-high heat.
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5
Add the onions and stir frequently until they are well browned, but not burned, 8 to 10 minutes.
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6
Turn down the heat to low and allow the pan to cool for 3 minutes.
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7
Add the parsley and ketchup, stirring to incorporate.
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8
Transfer the mixture to a small bowl and place in the refrigerator to cool.
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9
When the onion mixture is completely cool, combine it with the ground beef, chicken liver, matzoh, salt, bread crumbs, and eggs in a large mixing bowl and mix by hand until thoroughly incorporated.
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10
Roll the mixture into round, golf ballsize meatballs (about 1 1/2 inches), making sure to pack the meat firmly.
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11
Place the balls in the prepared baking dish, being careful to line them up snugly and in even rows vertically and horizontally to form a grid.
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12
The meatballs should be touching one another.
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13
Roast for 20 minutes, or until the meatballs are firm and cooked through.
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14
A meat thermometer inserted into the center of a meatball should read 165F.
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15
Allow the meatballs to cool for 5 minutes in the baking dish before serving.
