Heat a medium saucepan on medium-high heat then add the olive oil, onion, and garlic. Saute until fragrant and slightly wilted, about 2-1/2 minutes. Add the lentils, couscous, stock, lemongrass, sage, and soy sauce and bring to a boil. Reduce the heat and simmer uncovered for 10 minutes, then remove the pan from the heat. Cover the pan and let it sit for 10 minutes.

Transfer the mixture to a processor or blender, whizzing until pureed. When the puree is cool enough to handle, in about 4 minutes, form it into 12 firm 2" cakes. (To reheat, sizzle the cakes in a lightly oiled nonstick saute pan for about 1minute on each side.)