Prepare the potatoes: If using a large russet, slice very thinly on a mandoline to ~1 mm thickness and use a 1.5 cm (about 1/2 inch) ring cutter to punch small rounds. If using small Ratte potatoes, peel and slice them on a mandoline to the same thinness so pieces are roughly the same size.

Blanch the potato rounds in rapidly boiling salted water until just cooked through (they should be tender but not falling apart), about 2–4 minutes depending on thickness. Immediately transfer to an ice bath to stop cooking, then drain and pat dry.

Make a potato slurry: mix 1.5 tsp potato starch with 2 tbsp (30 mL) melted clarified butter to form a thin slurry. Gently toss the drained potato rounds in this slurry to lightly coat them.

Assemble the scales: Pat the flesh side of each fish filet dry. Arrange the potato rounds in overlapping rows over the flesh side of each filet to create scale-like coverage. Press a sheet of parchment paper over the assembled scales and press firmly so the potato rounds sit flush against the fish.

Set the scales: Put the assembled filets in the freezer for 10 minutes to firm up the potato scales (or place in the refrigerator for about 30 minutes) so they hold their shape when cooked.

Make the orange-veal reduction base: Finely chop the shallots. In a small saucepan, sweat the shallots in 1–2 tbsp clarified butter over medium heat until softened (1–2 minutes). Add the white wine, rosemary sprigs, and whole peppercorns and reduce the wine by about half.

Add veal stock and orange juice: Pour in about 400–500 mL of the veal stock (reserve the rest for another use) and the juice of the 2 oranges. Continue to simmer and reduce until the liquid is flavorful and slightly syrupy — this may take 10–20 minutes depending on the amount used. Taste and adjust seasoning.

Finish the sauce: Strain the reduction into a clean saucepan or bowl, discarding solids. Off the heat, whisk in the cubed cold butter, a few pieces at a time, to mount the sauce into a glossy emulsion. Stir in 2 tbsp crème fraîche to add brightness and body. Keep warm (do not boil) and check seasoning; add salt if needed.

Cook the fish: In a large nonstick or heavy skillet, heat 1–2 tbsp clarified butter over medium-high until shimmering. Place each filet scale-side down in the pan and cook without moving until the potato scales are golden and crisp, about 3–5 minutes (time will vary with thickness). Carefully flip the filet and cook the flesh side briefly — about 30–60 seconds — just to finish cooking through. Remove to a warm plate and rest briefly.

Serve: Spoon the orange-veal butter sauce onto plates and place the potato-scaled filets on top. Garnish with a little grated orange zest or a small sprig of rosemary if desired and serve immediately.