Preheat your oven to 375°F and line a baking sheet with parchment paper or a silicone baking mat. This ensures even baking and makes cleanup effortless. Having everything ready before you start mixing means your dough won't sit around and dry out while you're preparing the baking sheet.

In a medium bowl, combine the softened butter, sweetened condensed milk, vanilla extract, and fine sea salt. Beat or mix vigorously for about 1-2 minutes until the mixture is light, creamy, and well combined. The condensed milk acts as both a sweetener and binder, so it's crucial to incorporate it thoroughly with the butter to create an emulsion. I like to use an electric mixer here because the condensed milk can be sticky and mixing by hand requires real effort.

Add the sifted flour to the wet mixture and mix for about 1 minute until just combined into a soft dough. Don't overmix at this stage—you want a cohesive dough without tough, overworked gluten. The dough will be slightly sticky and tender, which is exactly what you want for these cookies.

Gently fold the semi-sweet chocolate chips into the dough using a spatula or wooden spoon, stirring just until evenly distributed throughout. I find it helpful to reserve a small handful of chocolate chips for pressing onto the top of each cookie later—this creates those gorgeous chocolate accents and adds texture.

Using a tablespoon or small cookie scoop, portion the dough into balls and gently flatten them into discs about 1/4 inch thick. Place each cookie on the prepared baking sheet, spacing them 2 inches apart to allow room for spreading. Press 3-4 reserved chocolate chips onto the top of each cookie for a decorative finish and extra chocolatey bites.

Bake for 12-15 minutes until the cookies are set and the edges are just beginning to turn light golden brown. The centers will still look slightly underdone when you remove them from the oven—this is perfect because they continue to cook on the baking sheet. Watch for the moment when the edges set but the centers are still soft; this keeps them tender and chewy inside.

Let the cookies cool on the baking sheet for 2 minutes to set slightly, then transfer them to a wire cooling rack to cool completely. This two-minute resting period prevents them from breaking apart when you move them, while the cooling rack allows air to circulate underneath so they don't become soggy on the bottom.