Mix flour, yeast, and salt in a bowl, then melt the butter and pour it into the water.
Pour the water/butter liquid into the flour mixture and mix it quickly.
Run in the mixer at medium speed with the dough hook for about 10 minutes until you have a cohesive dough that is a bit tacky. If it is too sticky, knead in a bit more flour by hand. It should not be dry.
Cover the bowl with a dishcloth and let the dough proof somewhere warm for about one hour or until the dough has doubled in size.
Shape the buns
Punch down the dough and divide it into ten pieces. Each piece should be about 88 grams.
Time to shape the buns: Hold the dough piece in your left hand (or right hand if you are left-handed). Fold the edge towards the middle of the bun, turn the bun about ⅛th and continue until the top of the bun is tight. Place the bun on an unfloured work surface. Place your hand over the top of the bun with your fingers like a spider. Move the bun around in circles to form a perfectly round bun. Look at this video to see it in action.
Place the buns on a baking sheet lined with baking paper and let them proof for about 20 minutes under a disk cloth.
Turn on the oven at 225°C / 440°F / Gas mark 8.
Prepare alkali bath
In the meantime, prepare the alkali bath. Please wear rubber gloves.
Pour 30 grams of sodium hydroxide into 4 cups of water. Stir with a wooden spoon until dissolved.
When you are ready to back, soak the buns in the liquid for one minute. Turn them around so that every surface has been exposed to the liquid. Take the buns out of the liquid with a slotted spoon, put them back on the baking paper, and continue with the rest of the buns.
Sprinkle sea salt on top and score a cross on the top of the bun using a serrated knife.
Bake the buns
Bake the buns for about 16 minutes or until they register an internal temperature of 99°C / 210°F.