How to Make It
Light a grill. Arrange the garlic halves cut side up on a sheet of foil and drizzle with 2 tablespoons of the olive oil. Wrap tightly.
In a large bowl, toss the carrots, spring onions and haricots verts with the remaining 1/4 cup of olive oil and season with salt and pepper. Grill the garlic packet, turning occasionally, until the garlic is tender when pierced, about 30 minutes. After 15 minutes, arrange the vegetables in a perforated grill pan and cook until tender and lightly charred, about 3 minutes for the haricots verts, 10 minutes for the spring onions and 15 minutes for the carrots. Transfer to a platter.
Unwrap the garlic and let cool slightly. Squeeze the cloves out of the skins and scatter over the vegetables. Drizzle with olive oil and vinegar and garnish with basil.