Prepare Potatoes: Cook the potatoes in salted boiling water for about 20 minutes, until fork-tender. Drain, peel, and mash until smooth.

Sauté Vegetables: In a skillet, heat sunflower oil and sauté onions and carrots until soft.

Cook Beef: Add ground beef, seasoning lightly with salt, and cook until browned.

Combine Mixture: Mix the sautéed beef and vegetables with mashed potatoes and egg yolks.

Shape Croquettes: Form the potato mixture into six balls or oval shapes.

Coat Croquettes: Dip each ball in potato starch, then egg whites, finishing with panko breadcrumbs.

Fry Croquettes: Fry in heated oil until golden brown, about 5 minutes.

Drain & Serve: Drain on paper towels and serve warm with Tonkatsu sauce.