Put potato chunks, butter, and sliced onions in the slow cooker and get a meal so delicious your family will be begging for more.

Prepare the potatoes: Peel the potatoes and cut them into roughly 1 1/2-inch chunks so they cook evenly. Rinse briefly under cold water to remove excess surface starch, then drain well.

Layer in the slow cooker: Place the sliced onion and minced garlic in the bottom of a 5- to 6-quart slow cooker. Add the potato chunks on top. Scatter the butter pieces over the potatoes.

Season and add liquid: Sprinkle the salt, pepper, and dried thyme (if using) over the potatoes. Pour the broth evenly over everything. The potatoes won’t be fully submerged; that’s fine, as they’ll steam and soften as they cook.

Cook until tender: Cover and cook on LOW for 5–6 hours or on HIGH for 3–4 hours, until the potatoes are very tender when pierced with a fork.

Mash in the slow cooker: Once the potatoes are tender, switch the slow cooker to WARM. Add the warmed milk or half-and-half and the sour cream (if using). Using a potato masher, mash the potatoes right in the slow cooker to your preferred texture—rustic with some chunks, or smoother if you prefer.

Finish with herbs and adjust seasoning: Stir in the chopped fresh parsley. Taste and adjust with additional salt and pepper as needed. If the potatoes seem too thick, add a splash more warm milk until they reach your desired consistency.

Garnish and serve: Sprinkle the sliced green onions over the top just before serving. Keep the potatoes on the WARM setting for up to 1–2 hours, stirring occasionally, until ready to serve.