Butter and flour a 9- x 12-inch baking pan and line with parchment paper.
Combine the chocolate, butter, coffee, and salt in the top of a double boiler or bowl over simmering water. Cook until melted and smooth. Let cool.
In a large mixing bowl, combine the sugar, eggs, and vanilla and whisk until smooth. Add the melted chocolate mixture and whisk until well combined. Fold in the flour until it just disappears. Gently fold in the pecans.
Pour into the prepared pan, smoothing the top. Bake about 35 minutes, or until a toothpick inserted in the center comes out clean.
Cool in the pan on a rack 1 hour. Run a knife around the edges of the pan to loosen and cut into squares. Lift out and transfer to serving dish or tin.