Antonie van Leeuwenhoek: Antonie van Leeuwenhoek, Dutch microscopist who was the first to observe bacteria and protozoa. His researches on lower animals refuted the doctrine of spontaneous
1 Rub the dripping or butter over the joint. 2  Season generously with salt and pepper. 3  Roast the beef topside according to your desired temperature: 20 minutes per 500g, plus an additional 20 minutes for rare; 25 minutes per 500g, plus 25 minutes for medium; 30 minutes per 500g, plus 30 minutes for well done. Roast the beef topside according to your desired temperature: 20 minutes per 500g, plus an additional 20 minutes for rare; 25 minutes per 500g, plus 25 minutes for medium; 30 minutes per 500g, plus 30 minutes for well done.
To cook it to medium-rare, or 135 F, subtract about 7 minutes per pound, for an estimated cooking time of a little over 1 1/2 hours. To cook the top round to medium-well, or 155 F, add about 7 minutes per pound to the medium estimate, for an approximate cooking time of a bit more than 2.5 hours. Because the meat's internal temperature is a fixed number, while cooking time is variable, use a meat thermometer to determine doneness definitively.