1 Scrub potatoes thoroughly. Cook in a pot of boiling salted water until knife-tender, about 20 minutes. Drain, rinse and peel while still warm. When potatoes are cool enough to handle, halve potatoes.
2 Meanwhile, peel onion and cut into rings, about 1 cm (approximately 1/2 inch) thick.
3 Rinse cherry tomatoes, drain and halve.
4 Rinse sorrel well, spin dry and cut into very thin strips.
5 Slit shrimp along the backs with a sharp knife or kitchen scissors to devein. Rinse shrimp, pat dry and season with salt, pepper and red-pepper flakes. Heat 1 tablespoon oil in a pan. Cook shrimp until seared, 1-2 minutes per side. Remove from pan.
6 Heat the remaining oil in the pan. Add halved potatoes and the onion rings and cook until golden brown, 4-5 minutes.
7 Add cherry tomatoes and cook until softened, about 1 minute. Season with salt and pepper.
8 Return shrimp to the pan and warm through over low heat. Mix in sorrel and serve immediately.