Prepare the court-bouillon: in a large pot combine cold Water with a halved and peeled Onion, a sliced Carrot, and chopped Parsley Root.
Add a tablespoon of whole Black Peppercorns, 2 Bay Leaves and a generous pinch of Salt. Bring to a gentle simmer and cook 15–20 minutes to extract the aromatics; keep the heat low so it never reaches a rolling boil.
While the broth simmers, peel and cut the Potato into even chunks and boil in salted water until just tender (about 12–15 minutes). Drain and keep warm.
Rinse and pat dry the Sterlet. Season lightly with a little extra Salt if you like.
Reduce the court-bouillon to a bare simmer, lower the heat so the surface is calm, then gently submerge the Sterlet. Poach for 8–12 minutes depending on size, until the flesh is opaque and flakes easily. Remove carefully and keep warm on a platter.
Make the herb dressing: finely chop fresh Dill and Flat-Leaf Parsley. In a small bowl whisk the herbs with the juice of one Lemon, a splash of Vodka (optional, for brightness), a pinch of Salt and a few tablespoons of the warm court-bouillon to loosen into a glossy dressing.
To serve, arrange the warm Potato on plates, lay pieces of the poached Sterlet over them, and spoon a little of the strained court-bouillon over the fish for moisture.
Drizzle the herb-and-lemon dressing over the fish and garnish with additional sprigs of Dill and Flat-Leaf Parsley. Serve immediately with lemon wedges on the side.
