Fried Squid With Aioli

Whisk potato starch, baking powder, and 3/4 cup arepa flour in a large bowl. Whisk in 2 1/3 cups water; let sit 30 minutes to allow flour to hydrate. Place remaining 1 cup arepa flour in a shallow bowl. Meanwhile, whisk egg yolk, garlic, and lemon juice in a small bowl to combine. Whisking constantly, gradually drizzle in grapeseed oil and olive oil; whisk until sauce is thickened and emulsified. Season aioli with salt; stir in 1 tsp. water. Fit a large pot with thermometer; pour in vegetable oil to come 3" up sides of pot. Heat over medium-high until thermometer registers 375 °F. Meanwhile, cut squid. Slice bodies lengthwise along one side and open to expose interior. Cut in half crosswise (or in thirds if large). Cut each half (or third) into 1 1/2" triangles; cut tentacles in half. Rinse; pat dry. Working in batches of 5 or 6 and returning oil to 375 °F between batches, dredge squid, scallions, and lemon in arepa flour, shaking off excess; dip into batter, letting extra drip off. Fry, turning every 30 seconds or so, until golden, crisp, and puffed, about 2 minutes. Transfer to paper towels; season with salt. Top with basil and serve with aioli.