Combine the active dry yeast with the tepid water and let it sit for about 5-10 minutes until frothy.
In a separate bowl, whisk together the all-purpose flour, sea salt, and half of the sugar (1/2 cup or 100g).
Add the frothy yeast mixture to the dry ingredients and stir until a rough dough forms.
Knead the dough on a floured surface for about 5-7 minutes until smooth and elastic.
Place the kneaded dough in a greased bowl, cover with a damp cloth, and let it rise for about 1 hour until doubled in size.
Pound the chilled salted butter into a rectangle between two pieces of parchment paper.
Roll out the risen dough into a rectangle, place the butter layer in the center, and fold the dough over to encase the butter.
Roll out the dough again, fold into thirds like a letter, wrap in plastic, and refrigerate for 30 minutes. Repeat this process two more times.
After the final fold, roll out the dough, sprinkle sugar, fold it in half, and roll out again. Cut into squares or circles and place in the baking pan.
Cover the shaped Kouign Amann and let rise for another 30-45 minutes until slightly puffed.
Preheat the oven to 375°F (190°C). Brush tops with melted butter, sprinkle sugar, and bake for 25-30 minutes until golden brown.
