5 ounces semisweet chocolate
8 tablespoons (1 stick) butter
1 1/2 cup sugar
3 eggs
1/4 tsp. salt
3/4 cup flour
1 1/2 tsp. vanilla
Preheat the oven to 350 F. Butter a 9-inch square cake pan. Melt the chocolate and butter in a pot on medium heat (or in a bowl set over simmering water), stirring until smooth. Remove from heat and transfer to a bowl; add the sugar, eggs, salt, flour, and vanilla. Stir well to combine. Spread in the pan and bake for about 40 minutes, until dry on top and almost firm to the touch.
When done, cool for about 15 minutes before cutting into 2-inch squares.