Lightly season ostrich with salt and pepper. Soak dried mushrooms in 600 ml(1 pints) warm water for 30 minutes, then drain (check no grit is clinging to them). Save the strained liquid for the polenta. Heat a frying pan (one with a lid) and add half the oil and the pumpkin. Cook over gentle heat for 2 minutes, tossing carefully, until pumpkin begins to colour. Mix in garlic, then cover and continue cooking, stirring occasionally, until pumpkin is tender. Remove pumpkin to a small bowl and wipe out the pan.
Put the pan back on the heat, and add remaining oil. Add ostrich steaks and cook 1 ½ minutes, then turn over. If your steaks are 1 cm(½ in) thick you’ll need to cook them for just another minute to have them medium-rare. Remove from pan and place on a plate, covered, in a low oven to keep warm.
Don’t wipe the pan, just add half the butter and when it stops foaming, add mushrooms and sauté until they’re cooked, adding a little salt at the end. Place on top of the ostrich in the oven.
Again, don’t wipe the pan but add remaining butter and leek and sauté until they’re wilted, then add 500 ml(16 fl oz) of the mushroom soaking liquid and bring to the boil. Turn to a simmer and scatter over polenta, whisking gently to prevent lumps forming, then bring to a gentle boil and stir for a minute. Add pumpkin, check seasoning and simmer another minute stirring continually.
Just as you’re about to serve, pour any juices that have come from the ostrich into the polenta and mix in. Dollop half the polenta onto each plate and sit the ostrich and mushrooms on top.