Clean and peel potatoes. Cut into 1-2 inch cubes and place into a bowl or pot of cold water (your water needs to be as cold as possible I add ice cubes). This will help get rid of the extra starch to prevent your potatoes from turning into gooey glue when mixing. Let soak for about 20 minutes.
Drain potatoes and rinse thoroughly. Fill large pot back up with water to cover potatoes and salt the water with about 2 teaspoon of sea salt and a bay leaf.
Place pot with potatoes on high heat and bring to a boil. Reduce heat to medium and cook until tender about 15 minutes.
Take off heat and drain water.
In a saucepan heat milk, butter, and salt until butter is melted DONT bring to a boil!
In a mixing bowl combine potatoes, egg yolks, and milk/butter mixture. Mix with a hand mixer on medium speed until creamy but don't over mix otherwise you will be left with a bowl of gooey potatoes.
Coat your casserole dish with butter or nonstick spray. Spread ¾ of mashed potatoes on the bottom and fill a piping bag with a 4B tip with the rest of the potatoes. Pipe any desired pattern.
Cover with plastic wrap and place into the refrigerator overnight or if serving the same day freeze for 15-20 minutes this will help the ridges not spread, but give you nice ridges.
Preheat oven to 375°f and heat through for 10-15 minutes. Broil for about 5 minutes until your ridges are a dark brown. Take out of the oven and top with a garnish like parsley if you want. Serve and Enjoy!
