Melt the chocolate, using a double boiler. Heat the evaporated milk in a small saucepan. Add the powered peanut butter and vanilla to the warm evaporated milk, and then slowly add the melted chocolate until fully incorporated and smooth. Do not let the mixture boil, or the cocoa butter will separate. Pour into a small dish lined with parchment paper. Spread the fudge fairly thin. Cool the room temperature or put it in the refrigerator. When cooled and set, cut into 2" x 2" pieces (1 ounce each) Try rolling into truffles topped with cocoa powder.