Bring a large pot of salted water to a boil. Add the diced potatoes and garlic to the pot. Cook covered until the potatoes are tender, which should take about 16-20 minutes.

Drain the potatoes and garlic, then return them to the pot. Stir in the low-fat sour cream, low sodium vegetable broth, and unsalted butter. Mash the potatoes using a fork, potato masher, or electric mixer until they reach your desired consistency. Season with salt and pepper to taste.

Serve the mashed potatoes warm, garnished with freshly chopped herbs if desired.