Here is how I made it:
I created the base covering a small balloon with papier mache. I made 3/4 layers and let it dry.
Now the fun/hard part (it depends on you!): I took a dish, anything big enough to contain the ball, and put some rice in it. I covered the ball with white glue then put it in the dish with the rice. Sticking the rice to the ball was pretty hard for me to do but after some time and with a lot of patience, I was finally able to cover the whole ball with rice.
Once dry, I sprayed gold paint on it...and voilà!