What is san nai in Bangladesh?

Bengali beef cooking is dominated by Kalo Bhuna (4-6 hour caramelization), Mezban (8-12 hour fat reduction), and Beef Tehari (slow rice-and-meat dum cooking) — all producing well-done results by default. The Bengali term 'Bhalo bhabe rana' literally means 'cooked well/properly' and is the cultural standard. Cow beef in Bangladesh (vs Buffalo elsewhere in the region) does allow for Medium-Rare preparations, and modern Dhaka steakhouses (Holey Artisan, Westin Dhaka) serve through the full doneness spectrum, but home cooking universally targets thoroughly-cooked. The fat-rich tradition (Mezban especially) requires extended cooking to render the Charbi properly — Medium-Rare in a Mezban context would be culturally illegible.