qiaoshiyang Try lowering your Youngs Modulus to maybe 7.5 for both layers. Seems like your fat layer is a little too stiff now, thus holding a lot of the thickness. In my experience, you need to allow it to compress a little more.
Similarly, try not using Poissons Ratio (Set to 0). Instead, you can try using Volume Conservation of 1 and lowering Volume Conservation Exp to 105. I find that it gives me better results than using Poissons Ratio.
And yeah, you'll need higher pressure (to suck it in) and surface tension (adjust accordingly with your final pressure setting to prevent the inner layer from getting sucked into the crevices too much).
Hope that helps!