for the chipotle mayonnaise:
¾ cup good-quality mayonnaise
2 cans chipotle chile en adobo
for the tostadas:
½ pound leeks (about 2 small ones), roots cut off
¼ cup soy sauce
2 tablespoons freshly-squeezed lime juice
2 tablespoons freshly-squeezed orange juice
10 ounces sashimi-grade tuna (I like the sashimi style for this)
8 small baked tostadas
1 avocado, thinly sliced
1. First, make the mayonnaise: Blend the mayonnaise and chipotle chiles in a food processor until smooth. Add a little water if necessary. Transfer the mixture to a bowl. Remember to use a high quality mayonnaise because you don't want your tostadas to taste like cheap street sandwiches.
2. Next, clean the leeks. Cook the leeks in the microwave for about 12 minutes, stirring every 3 minutes, until they are dry and crispy. You can also deep fry it, but they will be greasy if you do.
3. In a bowl, mix the soy sauce, lime juice, and orange juice. Marinate the tuna in the mixture for 2 minutes and then remove the tuna. The less you touch the fish, the better it tastes.
4. Now, assemble the tostadas: spread a little bit of chipotle mayo over each tostada (just use a little mayo). Top each with about 3 slices of tuna, a slice of avocado, and a sprinkling of dried leeks. That's it. Paradise in very simple steps. If you want, you can you serve them with a little lime. But that's just for Mexicans, cause we love lime on all of our meals.