The Canadian Forces' Boot, Extreme Cold Weather (also known as the Boot, Mukluk) comes in three parts: the white nylon-and-rubber outer boot, the insole, and the white cotton/wool 'sock' - essentially a sort of bootie that could, in theory, be worn separately as a sort of slipper, but in practice would get you yelled at. Assembly is straightforward; insert insole into boot, put on 'sock', put foot into boot, and lace. This latter is slightly different from your standard boot, as - to provide better ankle support, as well as to keep the mukluks on your feet - the laces have to pass through a tab at the back of the boot before being laced in front at the ankle. The result is a boot that - while having slightly less traction than the combat boot thanks to a lightly textured sole - is warm enough for temperatures and weather conditions where wearing combat boots would be detrimental to your podiatric health.
It also matches nicely with the other solid white Extreme Cold Weather equipment - that is to say, the Mittens, Extreme Cold Weather. (They do give you white snowpants and snowjacket, though.)