No. of Recommendations: 2
It's not obvious, and not really possible to add boards to favorites without some activity on the board. If you click on "Favourites & Replies"* at the bottom, you see it says this about favorite boards:
Recommending, or creating, a single post is enough for the board to reach your Favourites. To remove some of these boards from your Favourites, click the Customize icon above.
Your Love Factor is calculated with one point for every 10 post views by you, and one point for every 1 post recommended or posted by you. The boards listed above have all reached a Love Factor of 1.
So indirectly by viewing BRK.A posts, you will have added it as a favorite.
* Interesting spelling choice.