Something that gives you much happiness. Could allude to something unconventional as a source of happiness, since parsnips are rather under appreciated vegetables
Or, it could just be a totally nonsensical statement
1: Well, I'm perfectly content with life right now.
2: How so?
1: I have a parsnip.
2: ...What?
1: To have a parsnip is all I've ever wanted.
2: ...What?
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