Add 1 cup of water to the Pressure Cooker cooking pot and place steamer basket of chopped yams/sweet potatoes.
Lock on the lid and close Pressure Valve.
Cook at High Pressure for 4 minutes.
When Beep sounds, allow a 5 minutes Natural Pressure Release. Do not dump out water.
Mix together filling ingredients.
Remove yams/sweet potatoes from Pressure Cooker and place into a bowl. Add butter, egg, brown sugar, cinnamon, a slight dusting of nutmeg and a pinch of salt. Use an electric mixer and whip.
Pour 2/3 of the sweet potato mixture into greased casserole dish.
Sprinkle the filling evenly over the sweet potato mixture.
Gently spoon in the rest of the sweet potato mixture to cover filling.
Add an additional 1 cup of water to your Pressure Cooker cooking pot.
Lock on Lid and close Pressure Valve.
Cook at High Pressure for 13 minutes. When Beep sounds, do a Quick Release and then remove the lid.
Add marshmallows to the top of the Sweet Potatoes and place CrispLid over STAINLESS STEEL pressure cooker cooking pot. Set temp to 375 and time to 2 minutes. Alternatively, place casserole dish into oven and cook at under low broiler for 1-2 minutes, or until the desired color is reached.
Layer ingredients into a 2 quart slow cooker and cook on LOW for 5 hours. Add marshmallows and cook an additional 30 minutes.
Preheat oven to 350 degrees and cook for 30 minutes. Add marshmallows and place under LOW broiler until the desired color, about 1-2 minutes.
Air Fryer Method
Cook at 335 degrees for 20 minutes. Add marshmallows and cook at 400 degrees for 2 minutes more.
Use a 7 inch casserole dish (1.5 liters) for 6 quart or larger pressure cookers. Use a 7-9 inch casserole dish for 8 quart or larger pressure cookers and double the recipe for the 8 or 9 inch casserole dish.