How do I make the white parts of this cake? It's so precise it looks difficult if it's with royal icing.

Any ideas?

On the bottom cake the middle part of it looks like a stencil with RI and the rest like its piped. Dont know about the top tier

Looks to me to be a stencil. The way I know how to do these is with royal icing (although I think some use buttercream)

Basically, you just hold the stencil against the cake and lightly "paint / spread" the icing against the pattern. Then you peel off the stencil.

There are a couple you-tube videos on it.

As the others said, It's a combination of using a stencil, then accenting it piped dots.

I agree with everyone too... stencil and accent piping!