Sprinkle the gelatin over the water and let it soak (for about 20 minutes).
Combine the sesame paste, sugar, heavy cream, and soy milk in that order in a bowl, mixing as you go. Gradually stir these in little by little, especially the soy milk.
It should look like this after everything is added. (It's very watery.)
Boil some water in a pot, and place the bowl of gelatin over the pot of hot water.
Place the bowl of ingredients over the same pot of hot water to double broil.
When the gelatin has dissolved and the bowl of ingredients has slightly warmed, add the gelatin to the bowl of ingredients (keeping the bowl over the double broiler). Mix very well.
Gently pour into a mold to prevent air bubbles, and chill it in the refrigerator. After about 2 hours, it's done.
Here it is after it has set. I cut this into 6 equal pieces (my mold is 10.5 x 15 x 5.5 cm).
Black sesame version: With black sesame, the grains of sesame will be settle, so I stir it up once more after chilling it for a while.
Through trial and error, I figured out that heating the ingredients and the gelatin before mixing them together gives the goma dofu a great texture! For the sesame paste, you can use either white or black sesame.