Strain and cube grass jelly, spread half of it on jelly mold, set to side
In a pot, bring to boil, milk, water, sugar, and agar-agar. Pour half of it on grass jelly in the mold, chill in the fridge for 10 minutes
Spread more grass jelly, and pour the rest of the agar-agar mixture. Chill until set
When ready to serve jelly, about 10-20 minutes before serving, prepare the sauce
In a pot, mix everything until completely combined, then bring to boil, on low-medium heat. Mixture will be thickened
Serve pudding with room temperature, chilled, or slightly warm sauce