In a bowl mix the shrimp and lemon stir a a couple of times. Let the shrimps rest in the fridge for 5 minutes
Meanwhile, In a big enough bowl to contain the shrimp, mix the mayonnaise and mustard until even and smooth.
Add orange juice, shallots, chii and coriander.
Spoon the shrimps into the mayonnaise mixture and add the remaining lemon juice to taste along with salt and pepper if necessary.
Use a glass to make small circles in corn tortillas that are big enough to cover the bottom of muffin trays and have about 0.5 cm of an edge at least.
Brush some oil on the tortillas and bake for 5-7 minutes or until golden at 180 - 200 °C
This shrimp ceviche is best made fresh and up to 1 hour before hand. You can make the mayonnaise mixture beforehand and add the shrimp and lemon just before serving.