How to recreate the merging of gelatin I need to recreate the merging of white and colored gelatin:

I presume the process could contain these steps given a mold (powdered starch) to cast the product (facedown):

Pour fruity colored gelatin
Pour white gelatin after step 1 has dried a bit
To imitate the border, simply use a gradient as a mask between two Principled BSDF shaders.
As for the top material, glass with higher roughness works pretty well.