German Grune Sosse: Seven-Herb Sauce with New Potatoes and Farm Eggs

Put the new potatoes in a large pot, cover with cold salted water, and bring to a boil. Simmer 15 to 18 minutes, until a knife slides in with no resistance, then drain and let them steam dry in the colander.

Serves 4

Ingredients

• 2 pounds small new potatoes, scrubbed
• 6 large eggs
• 1 large bunch mixed fresh soft herbs, about 7 ounces total (parsley, chives, chervil, sorrel, borage, salad burnet and watercress)
• 1 1/4 cups full-fat sour cream
• 1/2 cup plain whole-milk yogurt
• 2 tablespoons sunflower oil
• 1 tablespoon white wine vinegar
• 1 teaspoon Dijon mustard
• 1 teaspoon sugar
• Fine sea salt and freshly ground white pepper, to taste
• Flaky salt, for finishing

Instructions

1. Put the new potatoes in a large pot, cover with cold salted water, and bring to a boil. Simmer 15 to 18 minutes, until a knife slides in with no resistance, then drain and let them steam dry in the colander.
2. While the potatoes cook, lower 4 of the eggs into a small pot of boiling water and cook exactly 9 minutes for firm-set yolks. Transfer to ice water, cool completely, then peel and halve lengthwise.
3. Hard-cook the remaining 2 eggs the same way. Separate the yolks from the whites — the yolks go into the sauce, and the whites get finely chopped for the garnish.
4. Wash and thoroughly dry all seven herbs, then pick the leaves from any tough stems. Chives and sorrel bruise easily, so handle them gently and keep the pile loose rather than packed.
5. Chop the herbs finely by hand with a sharp knife rather than blitzing them in a processor — the blades of a machine crush the leaves and turn the sauce a dull olive instead of bright spring green.
6. In a bowl, mash the 2 reserved cooked yolks with the mustard, vinegar, sugar and a pinch of salt until smooth, then whisk in the sunflower oil a little at a time to make a loose emulsion.
7. Fold in the sour cream and yogurt, then stir in the chopped herbs. Season with salt and white pepper, cover, and rest in the refrigerator for at least 30 minutes so the herbs perfume the whole sauce.
8. Halve any larger potatoes and arrange them warm on a serving platter with the halved eggs tucked among them.
9. Spoon the green sauce generously over the top, scatter with the chopped egg whites and a little flaky salt, and serve while the potatoes still have some heat in them.
10. Grune Sosse is the pride of Frankfurt and the Hessian countryside, so beloved that the city holds an annual festival in its honor and local markets sell the seven herbs pre-bundled in wax paper each spring and summer. The rule of seven is taken seriously — parsley, chives, chervil, sorrel, borage, salad burnet and watercress — but cooks argue endlessly about proportions, and every family insists their grandmother's ratio is correct. What makes it worth seeking out at peak harvest is that the sauce is only as good as the herbs in it: pallid supermarket bunches yield a flat, sour cream-heavy sauce, while a basket of just-cut market herbs gives something startlingly green, grassy and alive. It is traditionally served cold over warm potatoes and eggs, and the temperature contrast is the whole point.

Nutrition (estimated, per serving)

• Calories: 410 kcal
• Protein: 17g
• Fat: 23g
• Carbohydrates: 36g
• Fiber: 4g
• Sugar: 6g
• Sodium: 380mg