修剪茎端；保留细长尖端。冲洗，然后彻底擦干豆子——表面水分会导致蒸而不是烘烤。在大碗中与每磅1到1½汤匙橄榄油混合。用盐和黑胡椒粉慷慨地调味。可选：蒜粉、切碎的大蒜或切片的小葱。将任何帕玛森芝士保留到烘烤的最后几分钟。

Preheat oven to 218°C — fully up to temp before beans go in. Line a large rimmed sheet pan with foil or parchment. Spread seasoned beans in a single layer; no overlapping or crowding or they'll steam instead of roast. Large batches: use two pans, one on upper rack, one on lower. Roast at 218°C for 14–20 minutes. Thin beans (haricots verts): 14–15 min. Thicker beans: 18–20 min. Halfway through (7–10 min), shake the pan or use tongs to turn the beans. Swap rack positions if using two pans. Done when tender at center with lightly blistered, browned edges. Adding Parmesan? Sprinkle it on in the last 3–5 minutes and return to oven until melted and lightly crisp.

Done when tender but still holding shape, with browning or light char on edges and tips — color shifts from bright to deeper olive-green. Serve immediately; they soften as they sit. Key mistakes: overcrowding the pan (causes steaming, not roasting) and skipping the drying step after washing. Prep and toss in oil ahead if needed, roast just before serving. Leftovers keep refrigerated up to five days; reheat in a low oven.