Oh dear. I'm sorry about the shepard's pie.
I have a couple thoughts to save some of the leftovers. These are off the top of my head an may not work.
The cauliflower mash does tend to have a lighter texture than potatoes which isn't really as wonderful as potatoes. If you can scrape off the cauliflower/parsnip mash, you might mix in a bit of goat cheese and then rebake it. 2 tablespoons of a chevre would work for about 4 servings - more if you want the really cheesy flavor. I find goat cheese adds a bit of richness that is nice and would work well with the nutty taste of the parsnips as well as add a bit of weight to the frothiness of your mix. I would imagine that it would be tasty with a good steak.
I don't know how to help with the ground lamb if you don't like the flavor of lamb. Lamb does definitely have a different taste that some people just don't like. Personally, I love it but I do understand that it is different. Maybe you take the remainder and add an indian flavoring to it with lots of yummy veggies for a lamb curry. Lamb really lends itself to the strong spices of india. Also, I find lamb is really good cold - much better than beef as the flavor is much richer so you could give it a taste on it's own (sans parsnips) from the frig to decide if you really like it. If you t are willing to try lamb again at some point in the distant future, I would suggest buying a couple loin chops next time. They are pretty small and you need at least two to make a meal but they are really moist and delicious. Or - of course, making your boyfriend eat the lamb instead is always a reasonable option.
And, if my say has any value after trying the shepard's pie, I vote for wine and Puzzle Quest. Really, you deserve it.