Start by prepping everything so the cooking process is smooth. Finely chop cilantro and slice green onions, shred carrots, julienne cucumber into long noodle-like strips, and cut limes into wedges.
Mix dashi, soy sauce, sake, mirin, grated garlic, and jalapeño for the dipping sauce. Store chilled until serving.
For the shrimp, keep them cold while prepping, then peel and devein. Toss with preserved lemon, shallots, garlic, honey, vinegar, chili paste, salt, and pepper. Let marinate 10–15 minutes only.
Broil shrimp on a high oven rack for up to 8 minutes until fully cooked, keeping the oven slightly open with ventilation. Once done, immediately toss the shrimp in a quick herb mix of cilantro, green onion, shallot, olive oil, salt, and pepper.
Cook buckwheat noodles according to package directions, then rinse under very cold water to stop cooking. Keep chilled briefly if needed but avoid letting them sit too long or they will lose texture.
To serve, layer noodles in a bowl, add cucumber, carrots, and shrimp, then serve with dipping sauce and fresh lime wedges.