Heat oven to 350°F.
In mixer bowls, beat butter, sugar, flour, cocoa, baking powder, xanthum gum, eggs, milk, & 1 1/2 tsp vanilla. Spread in greased 13x9 pan.
Bake 40 minutes or until set.
Just before brownies are done, in saucepan, over low heat, melt chips with sweetened condensed milk & remaining 1 1/2 tsp vanilla. Immediately spread over hot brownies.
Cool. Chill. Cut into bars.