While the oil warms, place the garlic cloves on a cutting board. Slice the cloves in half lengthwise and then smash with the side of a chef's knife. Sprinkle a pinch of salt over the garlic and chop and smear the garlic against the cutting board until it makes a paste.
Place the grated plantains, garlic paste, and pepper in a large bowl and mix until combined. Using 2 tablespoons scoop out some of the mixture and press it flat with the back of the other spoon. Gently slide it in the hot oil, adding enough balls to fill the pan without overcrowding it. Fry until golden, for 4 to 5 minutes on each side (if the fritters get dark too quickly, lower the temperature of the oil). Using a slotted spoon or frying spider, transfer the aranitas to the paper towel-lined plate to drain. Sprinkle with some more salt and the cilantro and serve warm.