Melt butter and chocolate in low heat microwave. Set aside

Mix egg and sugar. Add vanilla, salt, chocolate mixture, marcarpone cheese. Stir with wooden spoon gently.

Add flour and cocoa powder. Stir gently until just mix

Pour in 9x12 inch greased pan (line in parchment paper)

Bake at 170C for 25 min. Once cool down, top the brownie with chocolate ganache (optional)