Combine the hearts of palm, red onion, cucumber and avocado in a large bowl and gently toss together.
Step 2
Combine the serrano chiles, cilantro, lime juice, olive oil, nori sheets (if using), and a pinch of salt in a blender and blend until completely smooth. You should have about 1 1/2 cups of liquid. Pour into the hearts of palm mixture and gently fold until all the ingredients are evenly coated. Marinate in the refrigerator until the onion and cucumber slightly soften, about 15 minutes. This dish is traditionally served right away, but can be covered and refrigerated for a day to allow the flavors to meld together. Serve with tortilla chips or tostadas.