Soak dried peeled split yellow mung beans in water for 4 hours at room temperature or overnight in the fridge.

Drain yellow water and rinse beans well.

Transfer beans to a saucepan, add fresh water about 1/8-inch above beans, and bring to a boil.

Reduce heat to medium and cook until the beans soften into a paste, stirring often to prevent burning.

Mash the beans in the saucepan or transfer to a microwave-proof dish and mash with a potato masher until smooth.

Sprinkle salt over the paste and mix well.

Add sugar gradually, adjusting to taste.

Spread the paste in a dish and microwave on high for 5 minutes to dry it out.

Set aside to cool.

For Dough #1, make a well in the center of the flour and add oil.

Combine with a fork until loose, coarse crumbs form.

Set aside.

For Dough #2, make a well in the center of the flour.

Whisk oil and water together in a separate cup and pour into the center of the flour.

Combine with a fork until the dough takes shape.

Divide into 4 parts.

Flatten each part into a square about 1/8-inch thick.

Crumble 1/4 of Dough #1 on top of Dough #2, spreading evenly but leaving space around the perimeter.

Gently roll up the square like a jelly roll.

Pinch the ends to seal.

Repeat with the remaining flattened squares.

Gently roll each jelly roll back and forth, stretching into a cylinder about 1-inch in diameter.

Place cylinders on paper towel and chill in the fridge for 30 minutes.

Preheat oven to 375°F.

Cut each chilled cylinder into 5 pieces.

Flatten each piece into a very thin square a bit less than 1/8-inch thick.

Place a small scoop of mung bean paste in the center of each square.

Fold the edges and pinch into a ball.

Place the ball pinched side down onto an ungreased cookie sheet and flatten slightly.

Brush tops with beaten egg.

Bake at 375°F for 20 minutes, or until the bottoms are slightly brown.

Store leftover hopia in Tupperware with a piece of bread to keep the pastry soft.