Tip:Be gentle when adding ingredients to the mashed potatoes—overworking will make the potatoes gluey.
Cut the potatoes into 1-1/2-inch chunks and put them in a large saucepan. Add 1 Tbs. salt, the bay leaf, garlic, and enough water to cover the potatoes by 1 inch. Bring to a boil over high heat. When the water begins to boil, lower the heat to a simmer and cook until the potatoes are completely tender when pierced with a fork, 15 to 18 minutes.
Drain the potatoes and garlic in a colander. Discard the bay leaf. Return the potatoes and garlic to the pan over medium heat and stir occasionally until they’re no longer steaming profusely (a little steam is fine) and the potatoes dry out, about 3 minutes. Mash with a potato masher (the mash should be somewhat coarse).
Heat the milk in a small saucepan or in the microwave on high for 1 minute. Add 1 tsp. salt to the milk, stir to dissolve, and, using a spatula, slowly stir the milk into the potato mixture. Stir in the parsley and olive oil. Season with several grinds of pepper and more salt to taste if needed.
If you’re not serving the potatoes immediately, keep them warm in a metal bowl covered with a saucepan lid. Put the bowl over a saucepan filled with an inch of simmering water and set over low heat.