Cut off the top and bottom of each plantain. Use a small paring knife to score the peel on the side that curves out, not going deep enough to pierce the flesh. Score the entire length of the plantain and pull off the peel. Discard.
Slice each plantain into 6 segments - roughly 1.5 inches apiece.
Combine lime juice and COLD water in a medium bowl and set aside. Place a few paper towels on a plate for your plantains to drain on after frying.
Pour oil into a dutch oven, cast iron, or other heavy bottomed pan. Place plantains in the oil - don't preheat! You want to start with cold oil.
Heat oil over medium heat and fry plantains for 11-13 minutes, rotating occasionally, until very lightly golden brown. If the insides are can be pierced with a fork, they're done.
Remove plantains from oil and place on a paper towel to drain. Leave the pot on the stove with the heat on.
Smash your plantains. If you don't have a tostonera, place a paper towel on a plate. Put a plantain on the paper towel and use another plate to smash it flat, until roughly 1/2 inch thick.
Repeat with remaining plantains. Once they're all smashed, quickly submerge each one in the lime juice / cold water bowl. Set aside while you finish the rest.
Pat each piece dry with a paper towel. In batches, fry smashed plantains for another 3-4 minutes or until crispy and deeply golden brown. Make sure not to overcrowd the pan. Remove from heat and drain on paper towel. Sprinkle with salt and pepper.
Serve with mojo. You can either serve the bowl of mojo for dipping, or pour the sauce over the top of the tostones.