Remove the tofu from its packaging and give it serval squeezes to remove as much water as possible. Cut the tofu into slabs about ½ inch thick.
Place a kitchen towel on your counter, then place a paper towel on top, then the tofu, then another paper towel and finally another kitchen towel. Place something heavy, like a textbook, on top.
Leave the tofu to press while you prepare the marinade.
Prepare the lemongrass by chopping of the stems and green leaves. You’ll be left with about ⅓ of the lower white part of the stem. Peel off the outer leaf. Slice the stalks into small rounds.
Add the lemongrass, cilantro, ginger, garlic, chili, soy sauce, brown sugar, 2 tablespoons of the oil and ½ tablespoon of water to a small food processor or the tall cup that comes with an immersion blender. Blend until you get a thick sauce without any fibrous bits.
Dice the tofu into cubes and place it in a bowl or container with a lid. Add about half the marinade along with an additional 2 tablespoons of water. Stir or shake to coat the tofu and set aside to marinade for at least 30 minutes up to overnight. Stir/shake from time to time to ensure the tofu remains evenly coated.
Heat 2 - 3 tablespoons of oil in a large pan over medium-high heat. Fry the tofu, flipping occasionally as it browns, until golden-brown on most of its sides.
Return the fried tofu to the bowl you marinated in and add 2 - 3 tablespoons more of the lemongrass sauce. Serve.