Combine lentils and 3 cups of water in a large saucepan. Bring to a boil, then turn heat down to medium and simmer until lentils are tender but not too soft, about 20 minutes.

Heat 1 tsp olive oil in a large, nonstick skillet over medium high heat.

Add mushrooms and cook until golden on both sides (about 2 minutes per side). You may have to cook in 2 batches in order to no overcrowd the pan.

Reduce heat to medium low, and add in the garlic. Cook for about 2 more minutes.

In a large bowl, combine the lentils, left green, mushrooms, lemon juice, and remaining olive oil.

Season with salt, pepper and red pepper flakes as desired, and serve immediately.