Preheat the oven to 400 degrees Fahrenheit. Line a large, rimmed baking sheet with parchment paper for easy clean-up.

Drain the lentils very well in a colander, then measure 2 ½ cups and spread them across a lint-free tea towel or paper towels to help dry them (if you have extra lentils, reserve them for another use).

To make the burgers: Cut the halved onion into a few slices before adding the onion and garlic cloves to the food processor. Pulse until the onions are roughly chopped, but no more.

Add to the food processor: towel-dried lentils, eggs, oats, handful of herbs (optional), chili powder and cumin, salt and black pepper. Process until the mixture has the consistency of chunky hummus (err on the side of caution here). Stir in the grated carrot by hand.

To prepare the burgers: Divide the lentil mixture into 8 equal portions using about ½ cup each. Shape them into patties about 1-inch thick. (If your mixture is unmanageably wet to shape, stir in a couple of tablespoons of your flour of choice, or more as needed.)

Brush both sides of each patty generously with oil and place them on the lined baking sheet, leaving a few inches of space around each one. Bake until the patties are deeply golden on the outside, about 35 minutes, flipping halfway.

To assemble the burgers: Toast your buns if you’d like. Top the lower bun with lettuce, if using, then a veggie burger patty, then spread a generous amount of guacamole or sauce on top. Top with crunchy condiments and tomato, and enjoy!

Leftover burgers keep well, refrigerated, for 4 days. Or, freeze them in a freezer bag for up to 3 months (thaw in the microwave for about 1 minute or in a 400 degree oven for 12 to 15 minutes, until warmed all the way through).