Display posts grouped by category and author

Hi
I am trying to do Group by Category and Author and display posts but have been unsuccessful. Single grouping works
Like I can either group by Author or Category but not both

Here is what I am able to achieve

Category Name 1
+ Post 1
+ Post 2
+ Post 3

Category Name 2
+ Post 4
+ Post 5
+ Post 6

Similarly I am able to do this
Author Name 1
+ Post 1
+ Post 3
+ Post 5

Author Name 2
+ Post 2
+ Post 4
+ Post 6

But I need to do this

Category Name 1
+ Author Name 1
+ Post 1
+ Post 3

+ Author Name 2
+ Post 2

Category Name 2
+ Author Name 1
+ Post 5

+ Author Name 2
+ Post 4
+ Post 6

Any help is highly appreciated.