From Korsnäs Finland. The caps that I saw as well as one pair of socks used the combination of knitting and tapestry crochet. The mittens however were knitted only with patterns that emulated the tapestry crochet patterns.
Ravelry: Korsnas hat course pattern by Marianne Kuokkanen. This technique is a combination of knitting and crochet. It’s not only a pattern, but instructions on how you can design a Korsnäs hat yourself.