Creamy Chipotle Shrimp Tostadas

Tostadas de Camarones Enchipotladas
Makes 50 "tostadas" or chips, enough for 12 to 15 as a pass-around appetizer
Recipe from Season 3 of Mexico - One Plate at a Time

The only thing I changed was that I didn't use squash blossoms and I couldn't find salad shrimp so mine were a bit bigger and I cut some of them up.
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Ingredients
1 large red ripe tomato
2 canned chipotle chiles en adobo, plus 2 tablespoons of the canning sauce
1 medium red onion, chopped into small dice
1 green onion, root end removed, then chopped finely
1 pound cooked, peeled, small "salad" shrimp (fresh has better flavor and texture than frozen; if frozen defrost overnight in refrigerator)
1 teaspoon chopped fresh thyme
2 to 3 tablespoons chopped fresh cilantro
3/4 cup crème fraiche, Mexican crema or homemade sour cream
Salt
A handful of squash blossoms (optional)
About 50 thick, homestyle tortilla chips or Guerrero-style chalupitas (or 20 to 25 4-inch crisp tostadas)
About 1/2 cup crumbled Mexican queso fresco or other crumbly fresh cheese such as salted, pressed farmer’s cheese or feta
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Directions
1. The shrimp mixture. Cut out the core of the tomato (where it attached to the plant), then cut in half widthwise. Squeeze each half gently to remove the seeds; discard. Cut tomato into 1/4-inch dice and scoop into a bowl. Remove the chiles from the can, then scoop the 2 tablespoons canning sauce into the bowl with the tomatoes. Slit open the chiles and scrape out the seeds. Chop chiles into small pieces and add to the bowl, along with the red onion, green onion, shrimp, herbs and crème fraiche or Mexican crema. Mix gently but thoroughly, then taste and season with salt (usually about 1 generous teaspoon).
2. Assemble and garnish the tostadas. If using the squash blossoms, pull off the little green sepals around the bottom of each flower, then carefully break off each flower from its base, dislodging the petals (they’ll stay together as a single unit) from the bulbous bottom; the pointy pistils inside should stay attached to the base. Cut the flower petals crosswise into thin strips.
Just before serving, pile a portion of the shrimp mixture onto each of the chips, chalupitas or tostadas and arrange on a serving platter. Sprinkle with the cheese and then the optional squash blossoms and serve right away.