Grease 8 of the cups in a muffin tin with nonstick cooking spray or softened butter.

To make the meatloaf, in a food processor, combine the onion, carrot, celery, parsley, and garlic. Pulse until the vegetables are very finely chopped. (You can chop the vegetables by hand instead; just really take your time so the vegetables are finely minced.)

In a medium bowl, combine the minced vegetables, ground beef, breadcrumbs, egg, Worcestershire sauce, salt, and pepper. Mix together well with your hands, but try not to compress the mixture too much.

Divide the meatloaf mixture evenly among the 8 greased cups of the muffin tin. Be careful not to press the mixture too firmly into the tin—leave it loosely packed.

Bake the meatloaf muffins until just set, about 20 minutes. Meanwhile, to make the glaze, in a small bowl, whisk together the barbecue sauce or ketchup, brown sugar, mustard, and cumin.

Remove the muffin tin from the oven and brush a generous layer of glaze onto the top of each meatloaf muffin (use all of the glaze). Return the muffin tin to the oven and continue to bake until the muffins are well browned and reach at least 165°F in the center of each muffin, 10 to 15 minutes.

Remove the meatloaf muffins from the oven and let cool briefly before removing from the tin. Serve with a grain, pasta, and/or veggie side.

Leftover meatloaf muffins will keep in the fridge for 3 to 4 days, or you can freeze them in an airtight container for up to 3 months.