1. Prepare a silicone mold (mine is diam. 3.5cm x 5mm deep) and place nutella on 12 molds. Flatten the surface. Freeze until firm (for a few hours).
2.Once nutella is firm, prepare the mochi In a bowl, add glutinous rice flour, sugar and a dash of salt. Mix. Then add tofu and water, mix with a rubber spatula until the dough comes together. Depending on the tofu and rice flour you use, the texture might change. So in case adjust the texture by adding more rice flour or tofu until you reach the target hardness which should be similar to an earlobe.
3. Transfer the dough to the working space and divide into 12 equal pieces.
4. Take one piece of dough and divide it in 2 halves. Flatten one of the 2 pieces. Take 1 nutella filling from the freezer and place it on the flattened mochi. Flatten the other one and place it on top, to cover the nutella filling. Stick them together.
5. Dust with potato starch lightly and shape nicely. Put it on a tray floured with potato starch. Repeat until you make 12 mochi.
6. In a frying-pan, pour a bit of vegetable oil, spread it with a kitchen towel, then heat the pan for 1 min over high heat.
7. Reduce the heat to low. Place a mochi on the pan and cover, cook for 5 min.
8. Remove the lid and flip the mochi. Cover and cook for 5 min on low heat.
9. Flip again and cook for 5 min on medium-low heat.
10. Lastly flip once more and cook 5 more min.
11. If not enough browned, then just flip them more until reaching a nice brown.
12. Remove from the pan when both sides nicely brown.