Place walnuts (or other nuts) on a pan and roast in the oven at 180C (350F) until fragrant, about 5 to 10 minutes. Pour the walnuts into a clean cloth and rub together to scrub off some peel. Put in a food processor and grind - but just until chopped, not until it is butter. 

Melt butter, pour over noodles and mix. Sprinkle over nuts and sweetener of choice.