In a small bowl, mix milk, sugar and yeast. Allow to sit in a warm place until mixture becomes frothy.
Sift together flour and salt then add polenta, butter, garlic, oil and the frothy yeast mixture. If needed, add enough of the extra milk to form a soft dough.
Knead dough on a floured bench until elastic then place in a lightly oiled bowl. Set in a warm place and let it double in size, about 1 1/2 hours. Punch dough down then knead again, until smooth. Shape into a loaf shape and set on a greased baking tray. Cut a few slits in the top then cover with a tea-towel and allow to rise an additional 20 minutes.
Bake at 400 degrees C for 10 minutes, reduce heat to 350 and continue to bake for 30 minutes.