Prepare the Pickled Cucumbers: Very thinly slice cucumbers lengthwise with a mandoline or a sharp knife, making 40 slices. Stir together vinegar, sugar, and salt in a small bowl until sugar is dissolved. Add cucumber slices, and toss to coat. Let stand 20 minutes; drain. Chill until ready to assemble meatball bites.

Prepare the Spicy Mayonnaise: Combine all ingredients in a small bowl; stir to blend. Set aside.

Prepare the Meatballs: Combine pork, scallions, garlic, ginger, soy sauce, fish sauce, mirin, and vinegar in a large bowl; mix gently with hands until incorporated, and form into 40 balls (1 tablespoon each). Spread panko in a shallow dish. Roll Meatballs in panko to coat, and place on a baking sheet lined with parchment paper.

Heat canola oil in a large skillet over medium-high. Cook meatballs, in batches, until cooked through and panko is crispy, turning often to brown evenly, 4 to 5 minutes. Transfer to a baking sheet lined with paper towels. Cover with aluminum foil to keep warm.

To assemble: Spread Spicy Mayonnaise on bottom of a large serving platter (or serve on the side in a bowl.) Fold 1 Pickled Cucumber slice, and skewer with a wooden pick; add 1 basil leaf, and 1 meatball. Repeat with remaining ingredients. Place picks, meatball side down, into mayonnaise.