In a large bowl, combine the dumpling flour, sugar, active dry yeast, and a pinch of salt.

Gradually add the warm water and vegetable oil to the flour mixture, stirring until a dough forms.

On a lightly floured countertop, work the dough for approximately 8 to 10 minutes until it achieves a smooth and elastic texture.

Transfer the dough to an oiled bowl, cover it with a damp towel, and allow it to rise for about an hour, or until it has doubled in volume.

After the dough has expanded, gently deflate it to release any trapped air.

Divide the dough into small portions, shaping them into oval or round buns.

Place the buns on a baking sheet lined with parchment paper and cover with a cloth.

Allow them to rest for an additional 20-30 minutes for a second rise.

Heat enough oil in a deep frying pan or pot over medium heat for deep frying.

Carefully add the mantou buns to the hot oil in batches, frying for 2-3 minutes on each side until golden brown and crispy.

Remove the fried mantou from the oil and place them on a paper towel-lined plate to drain any excess oil.

Serve the fried mantou while still warm, drizzled with sweetened condensed milk for dipping or drizzling on top.