Tiling on floor grade mastic asphalt

[Cringer]

I'm about to tile an area 2m X 10m in a kitchen area. The floor is covered with floor grade building mastic, hard, black, around 20mm thick.

I'm planning on using a decoupling mat after cleaning and using Sbr on the asphalt.

Part of the bitumen is uneven, to about 1cm over the 2m width. I'm not sure if, before applying the matting I should:

1. Attempt to reduce the uneven section. I'm not sure if it is safe either.
2. Can levelling compound be used over bitumen? I'm wary of using different substrates.

Any advice would be welcome.