1. Add the lentils to a medium saucepan and add water to cover by about an inch. Bring to a boil, then lower heat to a simmer and cook until tender, about 15 minutes. Drain and set aside.
2. Meanwhile, remove the excess water from the potato: you can either squeeze it by the handful, or put the entire pile on a clean tea towel and wring it out.
3. Crack the egg in a medium bowl and beat it lightly. Add the potato, cooked lentils, garlic, green onion, and cheese and hot sauce if you're using them in a medium bowl. Add the salt and a good grinding of black pepper, and stir until combined.
4. Heat a large skillet over medium heat, then add a generous drizzle of oil (1-2 Tablespoons). Working in batches, so as not to crowd the pan, add clumps of the potato-lentil mixture (about the size of a golf ball or slightly larger works well), and flatten each as soon as it's in the pan, making them about a half inch thick.
5. Cook for about 4-5 minutes per side, until the latkes are deeply golden brown and cooked through. Add a little more oil to the pan for each additional batch. Serve immediately or keep the latkes warm in a 200°F oven for up to an hour.