Slow Cooker French Onion Mashed Potatoes Step-by-step instructions

Before you start

Peel the potatoes and cut them into roughly 1-inch chunks. Slice the onions thinly. Measure the broth and have the onion soup mix ready.

You don't need to pre-cook anything; everything goes into the slow cooker raw. Make sure your slow cooker is at least 6 quarts to hold all the ingredients comfortably.

Instructions

Layer and Cook

1. 1Layer the ingredients
   Place the peeled and chunked russet potatoes in the slow cooker insert. Scatter the thinly sliced yellow onions over the top. Sprinkle the onion soup mix evenly over the onions and potatoes. Pour the beef broth over everything, making sure the liquid is mostly absorbed by the potatoes and onions but not completely submerged.
   Look for The potatoes should be coated with broth and seasoning, with some broth pooling at the bottom.
   Tip Use a spatula to gently toss the ingredients so the seasoning and broth coat the potatoes evenly.
2. 2Cook low and slow
   Cover the slow cooker and cook on LOW for 4 to 5 hours, or on HIGH for 2 1/2 to 3 hours, until the potatoes are fork-tender. The potatoes should be easily pierced with a fork, and the onions should be very soft and translucent.
   Look for The potatoes will be very tender and the liquid will be mostly absorbed; the onions will be caramelized and sweet.
   Tip Check at the lower end of the time range to avoid overcooking; the potatoes should hold their shape but yield easily.

After the first phase, the slow cooker should be filled with seasoned potatoes and onions.

The broth should be barely covering the bottom, and the onion soup mix should be evenly distributed. The raw potatoes will look pale and firm, but they'll soften during cooking.

Mash and Adjust

3. 3Mash the potatoes
   Turn off the slow cooker. Using a potato masher or a large spoon, mash the potatoes right in the insert until they reach your desired consistency. For a chunkier mash, mash briefly; for a smoother mash, mash thoroughly. The onions will break apart and streak through the potatoes.
   Look for The mash should be creamy with tender potato chunks and visible onion strands.
   Tip Do not over-mash or the potatoes may become gluey; aim for a rustic, slightly chunky texture.
4. 4Adjust the consistency
   If the mashed potatoes seem too thick, stir in a splash of warm beef broth or water until the desired consistency is reached. Taste and add salt and pepper if needed, keeping in mind that the onion soup mix is already salty.
   Look for The potatoes should be soft and spoonable but not soupy.
   Tip Start with a small amount of liquid and add more gradually; you can always thin the mash further.

The potatoes should be fork-tender and easily smashed. The onions will have cooked down into soft, sweet strands. The mash will be thick and creamy with some potato chunks remaining. The liquid should be mostly absorbed, leaving a rich, savory glaze.

Serve

5. 5Serve warm
   Spoon the mashed potatoes into a serving bowl. Serve immediately while hot, with additional black pepper or a pat of butter if desired.
   Look for The potatoes should be steaming and fragrant with onion and beef.
   Tip For a pretty presentation, drizzle a little melted butter over the top just before serving.

The mashed potatoes should be hot, steamy, and fragrant with onion and beef. The texture should be soft and spoonable, with visible onion streaks. Taste and adjust seasoning, then serve immediately.

Common mistakes

One common mistake is adding too much liquid, which can make the mash soupy. Start with the amount called for and add more only if needed after mashing. Another is overcooking the potatoes on high, which can make them waterlogged and gluey; low and slow is best.

Also, be careful not to over-mash, as that activates the starch and makes the potatoes gummy. Finally, don't skip the onions—they're essential for that French onion flavor.

How to tell it’s done

The potatoes are done when they are fork-tender: a fork should pierce a chunk with no resistance and the potato should start to fall apart. The onions should be very soft and translucent, almost jammy.

The liquid should be mostly absorbed, leaving just a bit of savory broth at the bottom. If the potatoes are still hard after the minimum cooking time, continue cooking in 30-minute increments until tender.