1. 1. Prepare the Potatoes: Start by peeling your russet or Yukon Gold potatoes. Once peeled, quarter them into roughly equal-sized pieces. This ensures they cook evenly. Place the quartered potatoes in a large pot.

2. 2. Boil the Potatoes: Cover the potatoes with cold water by about an inch. Add a generous pinch of salt to the water – this seasons the potatoes from the inside out. Bring the water to a boil over high heat, then reduce the heat to medium-low and simmer until the potatoes are fork-tender. This usually takes about 15-20 minutes. You should be able to easily pierce a potato piece with a fork without resistance.

3. 3. Drain Thoroughly: Once tender, carefully drain the potatoes completely in a colander. It’s important to get rid of as much water as possible to prevent watery mashed potatoes. You can even let them sit in the colander for a minute or two to steam dry slightly.

4. 4. Mash the Potatoes: Return the drained potatoes to the empty hot pot. Add the softened unsalted butter, minced garlic, and salt and pepper to taste. Begin mashing the potatoes with a potato masher. Mash until most of the lumps are gone, but don’t overmash at this stage.

5. 5. Add Dairy and Creaminess: Gradually pour in the whole milk (or half-and-half) and add the sour cream (or cream cheese). Continue mashing and stirring until the potatoes are smooth and creamy. Be careful not to overmix, as this can make the potatoes gluey.

6. 6. Adjust Seasoning and Serve: Taste the mashed potatoes and adjust the salt and pepper as needed. If you desire a thinner consistency, you can add a little more warm milk, a tablespoon at a time, until it reaches your preference. Serve immediately, garnished with fresh chives or parsley if desired.