In a mortar and pestle or a blender, add the chipotles and crush until smooth. Add some lime juice to help crush the chipotles. Once they are crushed, add the mayonnaise and stir.
In a deep pan, add the oil and wait for it to heat up. The temperature should read 300°F with a candy thermometer. Fry the leeks, stirring frequently with a wooden spoon until they start to brown and get crispy, about 2-5 minutes. Watch closely. Use a slotted spoon to remove the leeks from the oil. Add them on a plate lined with paper towel.
Bring the oil to 350°F. Fry the tortillas about 2 minutes on each side, until they are crispy. Add the tortilla on another plate lined with paper towel.
While the tortillas and leeks cool, add the tuna into a bowl, along with the olive oil, soy sauce, and orange juice. Let this marinate for 5 minutes.
Grab a tostada and spread the chipotle aioli over it. Top with marinated tuna, fried leeks and sliced avocado. Serve with lime wedges.
