Hi Eric. You shouldn't need to steam the spinach first, it's already been cooked. Also, make sure you squeeze as much water out of the spinach as you can.
I would make a roux of equal parts butter and flour, add the milk (not sure how much spinach you're using so it's hard to say how much flour, butter, and milk) stir over med heat until thickened. Pour over spinach, bake till heated through. And yes, parm would be great in this.
Like GG said, I would sprinkle the bread crumbs on the top rather than mixing it in.
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