Combine Milk and Sugar: In a heavy-bottomed saucepan, mix the milk and sugar over medium heat. Allow it to reach a gentle boil, stirring occasionally. Let it cook for about 20 minutes until it thickens slightly.
Add Walnuts: Incorporate the chopped walnuts into the mixture and continue cooking for an additional 10 minutes. The scent of toasted walnuts mingling with sweetened milk will start to envelop your kitchen, promising a delightful treat.
Cooling Stage: Remove the mixture from heat and allow it to cool down to around 110 degrees Fahrenheit. This cooling process is crucial for achieving the perfect fudge consistency.
Butter and Vanilla: Once the mixture has cooled sufficiently, add the softened butter and vanilla extract. Mix vigorously until the butter is fully incorporated, lending a creamy richness to the fudge.
Setting the Fudge: Pour this heavenly concoction into a prepared pan and let it rest until it solidifies. The anticipation builds as it transforms from a gooey delight to a firm, sliceable treat. Let it harden for a few hours, then cut, and serve.