Directions:

Place a rimmed baking sheet in oven and preheat to 400° F.

Rinse halved leeks and pat completely dry. Toss with olive oil and season with salt.

Arrange leeks, cut side down, on hot baking sheet and cover loosely with foil. Reduce oven temperature to 300° F. Bake until leeks are lightly browned on cut sides and very tender, about 1-1/2 hours.

Uncover leeks and turn cut side up. Increase oven temperature to 400° F; roast leeks until golden brown, 15-20 minutes.

(Reserve the oil for making vinaigrette or roasting vegetables. Let cool; cover and chill.)

DO AHEAD: Leeks can be baked 4 hours ahead. Let cool and cover.