Soak saffron threads in hot water in a bowl.

Melt 2 1/2 tablespoons butter in a pressure cooker over low heat. Cook and stir shallot until soft, about 3 minutes. Add rice; cook and stir for a few minutes until rice has absorbed butter and is toasted, about 3 minutes. Pour in wine and allow alcohol to cook off, about 1 minute. Add boiling stock all at once and stir. Close cooker securely and place pressure regulator over vent according to manufacturer's instructions. Increase heat to high. Heat until steam escapes in a steady flow and makes a whistling sound. Reduce heat to low and cook for 4 minutes.

Remove cooker from heat and release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Carefully open once pressure is completely released and stir well. Stir in saffron, remaining 1 1/2 tablespoon butter, Parmesan cheese, salt, and pepper.