What kind of cooling garnish is like ice cream but doesn't melt?
I'd avoid a coagulant if you can, it will likely keep this dense on whats already a rather dense sounding dish.

Personally, I'd beat loads of air into your sour cream/cream cheese mixture and serve a small whipped dollop of it.  It will keep it light and still offset your spiciness a little.  If the pork chili is the star, keep it complimented but not complicated.