Prions are essentially already denatured/unfolded. They are a more stable state of a normal protein that has biological function, and they interact with the "correctly" folded proteins to cause them to denature into additional prions. Often denaturing a prion means actually breaking apart the protein into fragments or amino acids, because it is already at the most stable/denatured state. This is also why they are so persistent in nature and so hard to remove from surfaces. Apparently gas plasma sterilization is a promising possibility. (this seems like an ok overview of the challenges: https://pubmed.ncbi.nlm.nih.gov/21271212/). Current procedures include things like autoclaving in 121C sodium hydroxide for 30 minutes. Definitely not something that fully cooking will inactivate.