I rarely use actual recipes for soups. I think a lot about flavor and color combinations, and go from there. Typically, you'll start with sweating some vegetables - a mirepoix - and be sure to have enough good stock on hand. Have fun!

Here's an easy soup "recipe" for sweet potato and parsnip:

Cut two medium sweet potatoes and two medium parsnips into 1/2 inch pieces; toss with butter (or duck fat for really incredible flavor) and roast at 400 degrees until the edges have begun to brown, about 40 minutes.

Meanwhile, sweat one white or yellow onion in a pan until the onion is soft, translucent and nearly all the moisture is gone. Add the vegetables to the pot with one can of coconut milk. Bring to a boil, reduce to a simmer and add salt and curry powder to taste. Puree soup with an immersion or regular blender. Voila!

The soup is somewhat sweet, but the curry balances it out.

I often use sweet potatoes and parsnip in my beef stew and they add a richness, not a sweetness. Also have roasted them and used them as a side dish. Fabulous.
https://www.cuisinart.com/recipes/soups/644.html has a recipe for sweet potato and parsnip soup that sounds great.