I found this!I do too. I had hatchery porcelain and sold all but one, and I don't breed her all her chicks had long necks, she is a good brooder, and I hope to use her to raise up quail next time she goes broody, which I hope happens twice next year.
https://www.backyardchickens.com/t/287781/gold-golden-neck-duccles
If it is correct, all you would need is a splash bird that is also homozygous for mille fleur. Technically, if you cross two blue mille fleur you would get 25% golden neck. Does that sound right? I thought I remembered reading that mf is autosomal recessive, and if that is the case, two mf should produce all mf, no? Add in blue genetics and 25% of those chicks should be splash, and if they are also mf they would be golden neck...