Not impossible at all, and no harder than a double recessive project. You would need Pied and Pastel on both parents.
For example, a pair of Pastel het Pied's could give you a super pastel pied - if you're very lucky. Haha
You could increase your chances if one parent was a super pastel (ie, super pastel het pied x pastel het pied), or if you were starting with a pastel visual pied.