Make the avocado relish for the filling: Cut the avocados in half, remove the pits and scoop the flesh into a medium bowl. Add the chopped cilantro if using, the lime juice, salt and olive oil. Use a fork to mash lightly until combined but still chunky. Transfer the relish to an airtight container and refrigerate immediately for later use.

Peel the plantains by first cutting off both ends. Using a small paring knife, make 3 to 4 shallow lengthwise slits along the peel, just deep enough to cut through the skin without piercing the flesh. Use your thumbs or the tip of the knife to gently lift and pry off the peel in sections.

Transfer the peeled plantains to a bowl of water to prevent browning. Slice into 2-inch-thick rounds. If not frying right away, place the plantain slices back in the bowl of water to prevent browning.

Dry the plantain sections well with a clean kitchen towel or paper towels before frying. Heat the neutral oil to 350 degrees F in a large Dutch oven or caldero. Fry the plantain pieces in batches for about 3 to 4 minutes, or until they are lightly golden. Remove and drain them on a paper towel.

To shape the cups, place a piece of parchment paper inside a citrus or lemon squeezer. Add one fried plantain piece, cover it with another piece of parchment and press down firmly on the squeezer to form a cup shape.

Fry the plantains a second time: Return the plantain cups to the oil at 350 degrees F and fry in batches until golden brown and crispy. Remove them from the oil and drain on paper towels. Sprinkle the tostones (fried plantains) with salt while they’re still hot.

When ready to serve, fill the tostones with a little spoonful of the avocado relish and then top each off with Vaca Frita. Garnish with chopped cilantro and a squeeze of lime wedge.

Place the flank steak in a large Dutch oven or caldero. Add the bay leaves and a generous pinch of salt. Add enough water to fully submerge the meat, about 10 to 12 cups. Bring to a boil over high heat, then skim off any foam or impurities that rise to the surface. Reduce the heat to medium low and simmer, covered, for 1 ½ to 2 hours or until the beef is very tender and easy to shred. If the meat is not tender add a bit more water as needed and continue simmering until it easily pulls apart.

Remove the flank steak from the pot and let it cool slightly. Shred the beef using two forks, then transfer it to a mixing bowl and season with the minced garlic, 2 teaspoons of the salt and the pepper. Use your hands to massage the seasoning into the meat until fully coated. You can continue to the next step right away, or you can cover your seasoned beef and refrigerate it for about 30 minutes to marinate and intensify garlicky flavor.

In a very large skillet, heat 4 tablespoons of the oil over medium-high heat. Add the sliced onions and cook for about 2 minutes, until starting to become translucent. Add the beef.

Spread the beef and onions evenly and cook over medium-high heat undisturbed for 3 to 4 minutes to develop a golden, crispy crust. If the mixture begins to look dry, add more olive oil. Add half the lime juice, stir, and then repeat the crisping again on this side. Add the rest of the lime juice and a little more olive oil if the pan looks dry or the beef isn’t crisping evenly. Continue this process for about 8 to 10 minutes total, or until the beef is deeply browned and crispy in parts. Taste and add more salt as needed.