Mix and sieve together the flour and baking powder onto a pastry board or cool slab. Make a well in the center and pour in the sugar, vanilla, rum, lemon juice, and the eggs. Draw in some flour from the sides of the well to mix with these and form a thick paste. Add the cold butter, cut into small pieces, the finely chopped beef drippings, cottage cheese, currants, sultanas, nuts and candied peel. Cover the fruits with more of the flour, and then starting from the middle, work all of it together quickly with your hands into a firm, smooth paste. If it should stick, add a little more flour. Form the mix into a long, oval shape, and then fold it over lengthwise to give it the traditional "stollen" shape. Line a baking dish with greased waxed paper and place stollen on this. Preheat the oven for 5 minutes at 500F. Then bake at a moderately hot over (375F) for 50-60 minutes. As soon as the stollen comes out of the oven, brush with melted butter and dust thickly with powdered sugar.