In a medium bowl whisk together the 2 ¼ cups all-purpose flour, 1 teaspoon kosher salt, and 1 teaspoon baking soda. Set aside.
In the bowl of your stand mixer, cream together the 1 cup unsalted butter, ¼ cup brown sugar, and ¼ cup granulated white sugar with the paddle attachment on medium speed until smooth.
Lower the mixer speed to stir and add in the ½ cup plus 2 tablespoons sweetened condensed milk and 2 teaspoons vanilla extract. Mix until thoroughly combined, about 30 seconds.
Stir the dry ingredients into the wet ingredients until just combined.
Fold in the 1 cup semi-sweet chocolate chips with a spatula. Wrap the cookie dough in wax paper and refrigerate for at least 3 hours to firm up the dough and allow the flour to fully hydrate.
Preheat the oven to 325°F (165°C). Line two large baking sheets with parchment paper or silicone baking mats. Set aside.
Roll the dough into balls, about 2 tablespoons of dough each. The dough may be a bit crumbly but will become smoother as you roll it.
Place the balls on the baking sheet leaving at least 2 inches in between each cookie. Sprinkle each one with sea salt.
Bake for 12 - 14 minutes or until the edges are lightly browned. Allow the cookies to cool for at least 5 minutes before transferring them to a wire rack to cool completely.
Notes
Measuring Ingredients: Using a digital kitchen scale is the most accurate way to measure your ingredients. If you don't have a kitchen scale you can measure the ingredients by volume but be careful when measuring the flour. Spoon the flour into the measuring cup and level it with the back of a butter knife. Try not to compress the flour into the measuring cup. Too much flour creates dense cookies.Salt: For all of my recipes, I use Morton Kosher Salt which packs more densely than Diamond Crystal Kosher Salt. If you are using Diamond Crystal Kosher Salt you will want to double the amount of salt you add.Butter: Room temperature butter is easier to cream together with the sugar. I use unsalted butter. If you only have salted butter you will need to omit the salt in the recipe. There is about ¼ teaspoon of salt per stick of salted butter.Evaporated Milk: Do not swap evaporated milk for sweetened condensed milk. They are two different things. Condensed milk is both sweeter and thicker than evaporated milk.Baking Sheet: These cookies are a bit sticky. Lining your baking sheets will make removal easier.Bake Time: For crispier cookies increase the bake time by 2-3 minutes.Storage: Baked cookies can be stored in an airtight container at room temperature for 2-3 weeks.Freezing Cookie Dough: Unbaked cookie dough balls can be frozen for up to 3 months. Place them on a parchment-lined baking sheet and freeze until solid. Once frozen, remove from the baking sheet and place in a zip-top bag. Label with the date and contents.When you are ready to bake cookies, remove the cookie balls from the freezer, let them sit at room temperature while the oven preheats, and then bake. You may need to add a minute or two to the baking time.