How to Make It
In a deep 4-quart (4-l) saucepan over high heat, bring the water and 2 teaspoons salt to a rolling boil. Working through each group in alphabetical and listed order (first the celery, then the chard, the haricots verts, and so on of Group A, then Group B, and then Group C), blanch each vegetable until tender. Each vegetable should take 2 to 3 minutes, depending on its size. Use the same water for all of the vegetables groups. As the water evaporates, the heat can be lowered to medium-high or medium, as long as the water remains at a healthy simmer. As each vegetable is ready, use a slotted spoon or spider to transfer to a colander and then rinse under cool running water and let drain. Transfer to a sheet pan lined with paper towel or a dishtowel to rest. Repeat with the remaining vegetables.
When all of the vegetables are cooked, remove the saucepan from the heat and reserve 1/2 cup (120 ml) cooking liquid for the sauce. Reserve the remainder for soup or stock.
Set a 12-inch (30-cm) frying pan over medium heat. Add the pancetta slices and cook, turning once, just until crisp, about 10 minutes total. Pour off the fat in the pan and reserve for another use. Add the reserved 1/2 cup (120 ml) cooking liquid to the pancetta in the pan, raise the heat to medium-high heat, and bring to a boil, scraping up any browned bits from the pan bottom. Boil until reduced to 1/4 cup (60 ml).
Add the butter and swirl to form an emulsion. Immediately add the vegetables and cook, tossing, until heated through and glazed with the sauce, about 2 minutes. Taste and adjust the seasoning with salt and pepper, then remove the pancetta if you like.
Artfully arrange the vegetables on a platter, drizzle with the sauce, and sprinkle with the herbs. Serve hot.
If you can’t find these exact vegetables, Paula offered many alternatives: Group A, spinach, green cabbage leaves, Brussels sprout leaves, asparagus, snow peas, zucchini; Group B, green garlic, ramps; Group C, celery root, beets. Sturdier vegetables such as the zucchini, celery root, or beets should be cut to 1/4-inch-thick matchsticks that can be cooked to tenderness within 2 to 3 minutes.
For a vegetarian version, omit the pancetta (in its stead, add about 1 teaspoon white or yellow miso paste with the butter at the final step).