Parsnips bring earthy interest to this potato mash. Infused oil elevates the easy side dish from expected to extraordinary.
Bring olive oil, peppercorns, bay leaf, rosemary, and cinnamon stick to a gentle simmer in a saucepan over low heat. Remove from heat, and let stand, covered, until cool. Strain. Meanwhile, cook potatoes and parsnips in a large pot of salted boiling water until tender, 20 to 25 minutes. Drain, then immediately mash with infused oil, salt, and nutmeg.