1. Preheat the oven to 350F.
 
2. In a saucepan, bring the milk and broth to a boil. Season with salt.
 
3. Gradually pour in the semolina, stirring constantly, and cook for 20 minutes or until thickened
 
4. Add parmesan cheese and half of the butter, mix well. Remove from heat, add rosemary, and set aside to keep warm.
 
5. In a pan, melt the butter. Cook the onions for 2 minutes. Cover and simmer over low heat for 4 minutes. Remove from heat and set aside.
 
6. Heat the olive oil in the pan. Add the pork fillet and sear until browned on all sides. Transfer the pork to a baking dish and bake in the oven for 15 minutes.
 
7. Once the pork is done, wrap it in aluminum foil and let it rest for 3 minutes.
 
8. Slice the pork into thick slices.
 
9. Serve the pork on a bed of caramelized onions, accompanied by creamy polenta.