Bring the maple syrup, sugars and baking powder to a boil over medium heat in a large pan. (Trust me, you'll need the large pan as the mixture will swell initially). Cook until a candy thermometer registers 240-degrees. Cool for 20 minutes. Then add the half-n-half, butter and vanilla to the mixture and beat well. Pour into a well greased pan. When completely cooled, cut into small squares.