Water in the oil can produce that effect. Hopefully it got there from condensation inside the filler neck but you should rule out the other, more serious sources. If it is a cracked head or blown head gasket you may be seeing some white smoke in your exhaust as well.
It is normal for people who drive short trips in the winter. Heat from the engine does not evaporate the normal moisture in the crankcase forming the yellow gunk. Go for a long drive!
It's a condensation mixtures of oil & water at the much cooler plastic oil filler tube end piece & cap, more pronounced in winter. BTW, it should not be more than half of a tea spoonful.