Cook Broccolini in a 6 to 8 quart pot of boiling salted water until the stems are crisp-tender, about 5 minutes. Drain in a colander, and then plunge into a large bowl of ice and cold water to stop cooking. Drain again and pat dry with paper towels.
Heat 1 ½ teaspoons oil in a 12 inch nonstick skillet over moderately high heat until hot but not smoking. Add half of garlic and ¼ teaspoon red pepper flakes and sauté until garlic is golden, about 1 minute. Add half of Broccolini and 2 tablespoons of stock and cook, stirring, 2 minutes. Transfer to a serving dish, then repeat with remaining oil, garlic, red pepper flakes, Broccolini, and stock. Season with salt.