Preheat oven to 350 degrees Fahrenheit. Grease a baking sheet.

Mash lentils or blend in a food processor. (If you’re trying to fool people into thinking this is meat, the lentil pieces left after mashing will be a dead giveaway, so use the food processor method.)

Heat oil/butter/shmaltz in a sauté pan over medium heat. Add the onions and cook until golden. Combine with lentils.

Add ground walnuts, eggs, garlic powder, salt, and mustard. Mix well.

Add matzah meal, flour, or breadcrumbs to bind the mixture so that you are able to shape into burgers that don’t fall apart. Adjust amounts as needed.

Using your hands, shape the mixture into burgers. Line on prepared baking sheet.

Bake for ten to twenty minutes, depending on size of burgers, until patties are solid on top.

Serve warm on buns with the usual hamburger toppings, such as ketchup, mustard, mayonnaise, lettuce, raw onion slices, or tomatoes.