How to Make It
Preheat the oven to 375°. In a pie plate, toast the hazelnuts for about 10 minutes, or until they are fragrant and browned. Transfer the hot nuts to a kitchen towel and rub them together to remove the skins. Let the nuts cool completely, then coarsely chop them.
Meanwhile, bring a medium saucepan of salted water to a boil with the smashed garlic. Add the shrimp and cook until opaque, about 2 minutes. Drain and let cool; discard the garlic.
In a large bowl, whisk the lemon juice with the minced garlic, 1/2 teaspoon of salt and a generous pinch of pepper. Whisk in the hazelnut and olive oils, then stir in the basil, celery leaves, scallion and 2 tablespoons of the chopped hazelnuts.
Coarsely chop the shrimp and add to the dressing. Season with salt and pepper and toss to coat.
Arrange the endive leaves on a large platter and spoon the shrimp salad onto them. Sprinkle with the remaining 1 tablespoon of hazelnuts and serve.