Rinse and dry all produce. Peel the plantains by slicing off the tops and then down one side; peel off the skin. Cut them into 1 inch thick pieces, on an angle. Cut the jalepeño in half and remove the stem and pith. Peel and roughly chop the shallot into quarters. Open the black beans and rinse well in a strainer. Juice the lime into a small bowl.
To make the chimichurri sauce, place cilantro (including stems), 1/2 of the jalepeño (or more if you like heat), garlic, lime juice, and shallot in a food processor or high speed blender. Pulse, adding 2 tablespoons of water to facilitate blending. Add vegan mayo and continue to blend on high until a thick sauce forms. Season with salt and pepper.
In a small pan over low heat, place drained black beans and spinach. Stir frequently to wilt the spinach. Season with salt and pepper.
In a sauté pan over medium-high heat, add 2 tablespoons of olive oil. Place plantains in the pan and cook for 2 minutes on each side, until they begin to brown. Flip and cook on the other side, then remove to a cutting board. Using the flat side of a knife, press down on the cooked plantain chunks to crush and flatten them. Season with salt and pepper and set aside.
In the same sauté pan, add 1 more tablespoon of olive oil and lightly toast the tortillas. We are looking for a crispy tortilla, but not to the point of browning or charring – about 1 minute on each side. Once these are finished it is time to prepare the tostadas.
To serve tostadas, place a tortilla flat on a plate and top with bean and spinach medley. Top with 3 slices of plantain and the chimichurri sauce. Serve and enjoy!