In a large mixing bowl, whisk together 3 cups all-purpose flour, 1.5 teaspoons salt, and 1.5 teaspoons instant yeast.

Pour 1 cup warm water and 2 tablespoons vegetable oil into the flour mixture and mix with a stand mixer fitted with a dough hook on medium speed for about 5 minutes or knead by hand for about 8 minutes until a shaggy dough forms.

Continue kneading for another 3 to 5 minutes until the dough becomes smooth and elastic.

Shape the dough into a ball, place it in a lightly oiled bowl, cover with a damp towel, and let it rise at room temperature for about 30 minutes until it has puffed slightly.

Turn the dough out onto a lightly floured surface, divide into 12 equal pieces, and flatten each into a 4-inch circle.

Mix 1/4 cup sugar with 1 tablespoon ground cinnamon, spread about 1 teaspoon softened butter on each circle, and sprinkle with the cinnamon sugar mixture.

Roll each circle tightly into a sealed ball, pinching edges to trap the filling.

Place the rolls seam-side down on parchment-lined baking sheets spaced about 2 inches apart and let rest for 10 minutes.

Gently flatten each ball into a 1/2-inch-thick disk using your palm or a glass.

Preheat the oven to 400°F (200°C) and bake the pan sobao for 18 to 22 minutes until the tops are light golden brown and the edges are deeply golden.

Remove from the oven and immediately brush each pastry with 2 tablespoons melted butter.

Transfer to a wire rack and let cool for 5 to 10 minutes before serving.