Do I need both an architect and a kitchen consultant?

For anything with a serious production kitchen, usually yes — they solve different problems. The architect owns the spatial and statutory design of the venue; the kitchen consultant owns production flow, the equipment schedule and food-safety zoning. Neither is appointed to do the other's job, and neither is appointed to reconcile the two — that reconciliation is the coordination work the owner's side of the table has to hold.

From Choosing Your Restaurant Architect, Kitchen Consultant and Contractor — the full reading, with the method behind this answer.