奶油猪仔包 Bun with butter & condensed milk

Curious why a simple bun with butter and condensed milk is named as  奶油猪仔包? I googled and this is what I get:

 奶油猪仔包，也叫奶油猪、奶油脆猪，蜕变自“奶油多士”（炼奶牛油多士），用烘烤香脆的猪仔包，切开两半，涂上牛油和炼奶便成，在香港一些茶餐厅供应.

Toasted soft and fragrant bun spread with butter and topped with condensed milk 

simple ingredients and preparation yet so tempting delicious!

RM2 per bun at Min Feng Hao 民豐號