In a medium saucepan, bring 1 quart of salted water to a boil and add 2 tablespoons of the lime juice. Add the shrimp, cover and return to a boil. Immediately remove from heat, set the lid askew and pour off all of the liquid. Replace the cover and let the shrimp steam off the heat for 10 minutes. Spread out the shrimp in a large bowl to cool completely. Toss the shrimp with the remaining 1/2 cup lime juice, cover and refrigerate for 1 hour.: The moment the water comes to a rolling boil you will smell the faint citrus lift, which helps temper the cooking water so it does not overwhelm the shrimp. The boiling point gives a quick, even heat that cooks the shrimp through without overcooking. A common mistake is leaving the shrimp in the hot water too long, which makes them rubbery, so watch the clock and proceed right away.
In a small strainer, rinse the onion under cold water, then shake off the excess liquid. Add the onion to the shrimp along with cilantro, ketchup, hot sauce, olive oil, jicama, cucumber and avocado. Taste and season with salt (about 1/2 teaspoon). Cover and refrigerate if not serving immediately.: When the shrimp hit the water you will often hear a soft hiss and see the surface agitate, signaling rapid heat transfer. This quick contact with boiling water firms the flesh and sets the color. Avoid crowding the pan, as overcrowding lowers the temperature and can produce unevenly cooked shrimp.
Spoon the ceviche into small bowls or martini glasses, garnish with cilantro sprigs and slices of lime. Serve with tortilla chips.: Removing the saucepan from heat stops the active cooking, and pouring off the liquid prevents the shrimp from continuing to poach in residual heat. You should notice the shrimp shift from translucent to opaque, a visual cue the proteins have tightened. Do not leave the liquid in place, or the texture will tighten too much and become tough.
Replace the cover and let the shrimp steam off the heat for 10 minutes: During this resting period the shrimp finish cooking gently, and the steam keeps them tender rather than jerky. You will feel residual warmth when you lift the lid, and the aroma will be savory and slightly citrusy. A frequent error is shortening this rest, which results in undercooked centers, so be patient with the full ten minutes.
Spread out the shrimp in a large bowl to cool completely: Spreading the shrimp prevents carryover cooking and helps them cool faster so they are ready to absorb the marinade. As they cool, they lose some steam and the texture firms just enough. Leaving them piled up traps heat and continues cooking, so be sure they are in a single layer for efficient cooling.
Toss the shrimp with the remaining 1/2 cup lime juice, cover and refrigerate for 1 hour: The sharp, fresh scent of added lime juice signals the start of the curing process, where the acid alters the shrimp s proteins and brightens flavor. This hour allows the acid to permeate the shrimp without making them mealy. Skipping the chill or shortening it reduces flavor infusion, so aim for that full hour for best results.
In a small strainer, rinse the onion under cold water, then shake off the excess liquid: Rinsing softens the raw bite and removes excess sulfur notes, leaving crisp, clean onion pieces. You will notice a milder onion aroma afterward. Forgetting to rinse can leave the onion overly pungent, overshadowing the delicate shrimp and herbs.
Add the onion to the shrimp along with cilantro, ketchup, hot sauce, olive oil, jicama, cucumber and avocado: At this stage the bowl becomes a chorus of textures and scents, from herbaceous cilantro to creamy avocado . Stir gently so the ingredients combine without mashing the avocado. The olive oil will mellow the acidity and the ketchup will add gentle sweetness. Overmixing will bruise the avocado and make the mixture visually unappealing, so fold carefully.
Taste and season with salt (about 1/2 teaspoon): Seasoning activates the flavors, and you will notice the difference immediately when salt balances the acid and sweetness. Start with a modest amount and adjust after the ingredients have rested a bit. A common misstep is over-salting early, which can be hard to correct once the flavors have fused.
Cover and refrigerate if not serving immediately: Chilling harmonizes the flavors and tightens the overall texture, offering a cool, refreshing profile when served. The bowl should smell clean and bright with a subtle herb and lime perfume. Leaving it at room temperature for too long risks losing the crispness of the jicama and cucumber and increases food safety concerns, so refrigerate if there is any delay.
Spoon the ceviche into small bowls or martini glasses, garnish with cilantro sprigs and slices of lime: Presenting the ceviche in small vessels makes it feel special and contagious at the table, while the garnish adds an aromatic top note. You will see the avocado and shrimp colors pop against the green cilantro. Avoid overcrowding the presentation, which can compress textures and reduce the visual appeal.
Serve with tortilla chips: The chips add a satisfying crunch and act as a vehicle for every layered bite, providing contrast to the cool ceviche. Serve chips on the side so guests can scoop without sogginess. Placing the chips directly in the bowl too early will cause them to soften and lose their crunch.