They're cute little bantams.I have never heard of the Millie Fleur D’Uccles.
The breed is called d'Uccle, named for the town of Uccle in Belgium, where they originated. The breed comes in several different color varieties.
"Mille Fleur" is French for "thousand flowers," obviously referring to all the little white and black dots. Mille Fleur varieties exist in a few other breeds as well.