Rinse the lentils, and then set them to boil in a large saucepan or pot, in just enough veggie stock to cover.
While they're boiling, chop up the potatoes and onions.
Place the potatoes, onions, garlic and all spices in a large skillet and put enough olive oil on to cover or to taste. Sautee on medium-high heat for about fifteen minutes, or until onions are tender.
Add the potato/onion mixture to the boiling lentils. Add a bit more veggie stock, if needed (the whole thing should have enough liquid to boil, but not stew).
Boil the mixture for thirty minutes or so, until the liquid becomes thick and gravy like. Add more salt/garam masala to taste.
I serve this over puri or naan. I usually have a side of raita, for those of you who eat yogurt. Its also good with a few lemon wedges squeezed over it.