In a large mixing bowl, combine the room temperature water and instant yeast. Stir gently to dissolve the yeast. Next, add the all-purpose flour and salt into the mixture. Use a spatula or your hands to mix until a shaggy dough forms.
Transfer the dough onto a lightly floured surface. Knead it for about 5-7 minutes until it becomes smooth and elastic. Form the dough into a ball and place it back into the mixing bowl. Cover it with plastic wrap and let it rest at room temperature for about 1 hour, or until it doubles in size.
While the dough is resting, prepare the chilled cubed butter. Place the butter between two sheets of parchment paper and use a rolling pin to flatten it into a rectangle about 1/2 inch thick. Chill the butter in the refrigerator while the dough rises.
Once the dough has doubled, punch it down to release the air. On a floured surface, roll the dough into a large rectangle, about 12x18 inches. Place the chilled butter in the center of the dough. Fold the dough over the butter, encasing it completely.
Roll the dough out again into a larger rectangle. Fold it into thirds like a letter, then wrap it in plastic wrap and chill for 30 minutes. Repeat this rolling and folding process two more times to create layers.
After the final fold, roll the dough out into a rectangle again. Sprinkle half of the granulated sugar over the surface. Cut the dough into squares (about 3x3 inches). Fold each square into a triangle and place it in a greased muffin tin, standing upright.
Cover the muffin tin with plastic wrap and let the pastries rise for another 30-45 minutes until puffy.
Preheat your oven to 375°F (190°C). Sprinkle the remaining sugar over the top of each pastry. Bake for 25-30 minutes until they are golden brown and caramelized.
Allow the Kouign-Amann to cool in the pan for about 10 minutes before transferring to a wire rack. Enjoy them warm for the best experience or at room temperature, where the layers will still be wonderfully flaky.
