Preheat oven to 165°C (330°F). Cut mozzarella into cubes or half spheres if using bocconcini and place them in a silicone mold.
Bake for 3 minutes, just until the cheese is soft (do not let it melt fully).
Remove from oven. Do not dry the water released by the mozzarella. Let sit 1 minute at room temp, then gently press down with your fingers or the back of a spoon to shape it.
Let cool a few minutes in the mold or place in the fridge to set.
Once firm, remove carefully and transfer to a bowl of cold water until ready to serve.
Method 2 – Microwave:
Place a slice of mozzarella (not the whole ball, just a tranche) in a heatproof bowl. Microwave for 15 seconds or just until pliable.
Stir gently to form a stretchy dough, then carefully pick it up (let it cool slightly if too hot).
Tear small pieces, press them into the mold, and smooth down.
Let them set at room temperature or in the fridge.
Remove from mold and place in cold water until serving.