Make the meatballs first. You can bake the meatballs or use an air-fryer. If baking, preheat the oven to 375 ℉.
Make a flax egg. Whisk together the flax meal and water. Set aside for 3-5 minutes or until it has thickened.
In a large mixing bowl, mash the lentils with a fork or potato masher, then add the flax egg you made, the breadcrumbs, olive oil, liquid smoke, soy sauce, garlic and onion powder, and a pinch of salt and pepper.
Stir everything together until fully combined, then roll the mixture into balls. If baking, place the meatballs on a large sheet pan sprayed with non-stick spray, then bake for 10 minutes, flip the meatballs and bake for about 10 more minutes. ,
If air-frying, spray the basket with non-stick spray and air-fry for 8-10 minutes, flipping the meatballs half way through.
While the meatballs cook, make the gravy. Heat the olive oil on medium-high in a large non-stick skillet.
Add the onion and garlic, reduce heat to medium, and saute until the onions are starting to brown, about 5-7 minutes. Add the thyme sprigs and brown sugar, stirring everything together.
Continue to saute until the onions are golden brown, about 5-7 more minutes. Add the flour and stir it into the onions.
Pour in the broth and a pinch of salt and pepper. Whisk to combine. Bring to a simmer, and let simmer for about 5 minutes, whisking frequently. The gravy should thicken up.
Remove the thyme sprigs, taste, and adjust the seasoning. Adding more salt and pepper as needed. I like to add a splash of balsamic vinegar if it needs acid.
Add the cooked meatballs to the skillet and toss them in the gravy.
Serve immediately over mashed potatoes if desired.