Fry tortillas in oil over medium heat until blistered, golden brown, and very crispy. Blot lightly on a paper towel, and sprinkle with salt if desired. Place on a cooling rack and let cool fully. Store in an airtight container until needed.

Remove all but one tablespoon of the oil from the pan, and set heat to medium high. When hot, add shrimp and sear each side for just 30 seconds. The shrimp should still be almost raw inside. Remove and let cool for 5 minutes.

Cut shrimp into small pieces, and add to a bowl. Add lime juice, chipotle, cumin, paprika, salt, olive oil, and ketchup. Mix well, cover, and transfer into the fridge for 1 to 8 hours.

To make avocado spread, mash avocado and salt with the back of a fork until it’s as smooth as you want. Stir in lime juice, jalapeño, and cilantro. Refrigerate until needed.

Remove shrimp from the fridge and mix in the red onion, tomato, cucumber, and cilantro. Taste for salt and adjust as needed.

To make tostadas, spread crispy tortillas with avocado spread, and top with the deviled shrimp. Finish with a drizzle of Mexican crema or thinned out sour cream.