I was going to suggest chicken in dijon tarragon sauce over mashed potatoes, but you said no dairy. I usually use half and half to make this but mix it with stock, so maybe you could use all stock?
DS is dairy free and we find that hemp milk or quinoa milk work well in mashed potatoes, along with a vegan butter-like-spread in place of butter. I bet you could do half stock and half non-dairy milk and you'd be OK.
Also, your idea sounds awesome. I would add asparagus chunks.