Preparation Place potatoes in a medium pot; add cold water to cover by 1". Season with salt, bring to a boil, and cook until potatoes are fork-tender, 12–15 minutes. Transfer to a large bowl of ice water and chill until cold, about 3 minutes. Transfer to paper towels and pat dry, reserving bowl of ice water. Meanwhile, bring another medium pot of salted water to a boil. Add green beans and cook until crisp-tender, 2–4 minutes. Using a slotted spoon, transfer beans to ice water; reserve hot water in pot. Chill beans until cold, about 3 minutes. Transfer to paper towels and pat dry, reserving bowl of ice water. Return water in green bean pot to a boil, carefully add eggs, and cook 8 minutes. Using a slotted spoon, transfer eggs to ice water; reserve hot water in pot. Chill eggs until cold, about 5 minutes. Peel; set aside, reserving bowl of ice water. Return water to a boil, add shrimp, and cook just until pink, about 3 minutes. Transfer to ice water and chill until cold, about 3 minutes. Transfer to paper towels and pat dry. Meanwhile, pulse garlic in a food processor until finely chopped. Add egg yolks, lemon juice, and mustard; season with salt, then process to combine. With the motor running, slowly pour in grapeseed oil a few drops at a time. After about 1/4 cup has been added, scrape down sides of bowl with a rubber spatula. Continue to add grapeseed oil with the motor running, then add olive oil and process until combined. If sauce is too thick, add water 1 Tbsp. at a time. Taste and add more salt and lemon juice, if needed. Transfer aioli to a serving bowl. Arrange potatoes, green beans, shrimp, halved eggs, endive, romaine, radishes, cucumbers, and tomatoes on a platter and serve alongside. Do Ahead Potatoes, green beans, and eggs can be cooked 2 days ahead. Transfer to an airtight container and chill. Aioli can be made 1 day ahead. Transfer to an airtight container and chill.