Leaf broccoli produces strongly-flavored greens, and soup would be a good application for them. And they are very cold-hardy.
Mine over-wintered in Zone 8, often covered with ice and snow, them flowered next spring. I saved a lot of seeds, will share for postage. Or join the Piggy Swap.
Broccoli (Brassica oleracea 'Spigariello')
Spigariello Liscia = Broccolo Spigariello = Brassica oleracea var. 'Spigariello'
Very cold-hardy. Full Sun Annual (I got seeds the second year)
Italian Heirloom O.P. 45-65 days
12" - 24" tall
16"- 24" spacing
deep blue-green leaves & tops: sweet, strong broccoli / kale flavor
Strip center rib off old leaves. Cooked leaves freeze well