The coffee bun is basically a soft enriched bread roll with a cold butter core and a crunchy coffee-flavoured cream topping that bakes into a shell. Think of it as a hybrid between a dinner roll and a pastry. If you have never had one, the appeal is real: you bite through the slightly crisp top into soft bread, hit that pool of melting butter in the middle, and it just works. The 340 calories in one bun come from three layers of calorie-dense ingredients: the enriched dough made with egg, milk and sugar (190 cal), the butter filling (72 cal from just 10g of butter), and the coffee cream topping (78 cal from another hit of butter plus sugar). To be straight with you, hard calorie data on these buns is thin, so treat this 340 figure as a solid ballpark estimate, not a lab-verified number. The actual count can shift depending on how generous the baker is with the butter core.
Where the maths gets interesting is in how many you eat. One bun at 340 cal is a decent snack. Two buns is 680 cal, which is already a full meal worth of calories in something you ate standing at a kiosk in 4 minutes. The butter filling varies a lot too: some places are stingy (maybe 5-7g butter, closer to 35-50 cal) while others are extremely generous (15g butter, pushing 107 cal). That single variable alone can swing the bun by 50 to 70 calories. If you are in a deficit and want one, eat it fresh and hot so one bun is genuinely satisfying, and skip the teh tarik or kopi that usually comes alongside it.