Suntory Premium Malt's Dark

Suntory's Premium Malt's Dark is listed as a limited or seasonal product, but fortunately it seems to be available pretty often. On the website it give directions on two ways to mix this dark version with the regular version to create either white or dark bubbles. The trick is to create the desired color bubbles first by pouring either the regular or dark beer directly down the middle of the glass and then pour the other beer down the side of the glass.

http://www.suntory.co.jp/beer/premium/black/index.html?fromid=beer_top_pc

Photo is a web capture for explanatory purposes, copyright belongs to the company.