Add shiratamako, sugar, water, and vanilla bean paste in a bowl. Mix to combine.
Transfer mochi batter to microwave safe bowl (I line my bowl with a damp washcloth) and cover well with plastic wrap, another dish, or other cover. Microwave for 2-3 minutes or until mochi becomes evenly translucent.
Carefully dump cooked mochi onto a surface lightly dusted with katakuriko. Divide into six pieces. While you work with one piece, keep the others covered with a damp cloth so they don't dry out.
Flatten one piece (either with a small rolling pin or your hand) of mochi dough. Place a teaspoon of Nutella in the center and gently spread, but do not push the Nutella all the way to the edges.
Place a strawberry in the center of the Nutella.
Wrap the mochi around the strawberry, pinching the edges to seal. Dust in katakuriko.
Repeat for the rest of the 5 pieces. Daifuku is best eaten the day it is made.