Preheat the oven to 350°F/180°C. Line cookie sheets with baking parchment paper.
Add the butter and sugar to a mixing bowl and cream together by beating with an electric mixer or stand mixer until light and fluffy.
Add the condensed milk and vanilla and beat again.
In a separate bowl, sift the flour, baking powder and salt together. Then stir it into the butter mixture, a little at a time.
Stir in the chocolate chips.
Roll teaspoon-sized balls of the condensed milk cookie dough and place them onto the prepared cookie sheets. Press each one down slightly with a fork or the heel of your hand.
Place the cookie sheets in the oven and bake the cookies for 8-10 minutes or until they just begin to turn slightly golden, but don’t overbake them.
Allow the cookies to cool on the trays for 5 minutes, then gently transfer them to a wire rack to cool completely.
Notes
For best results, make sure your butter is at room temperature before you begin baking. This helps to ensure that your ingredients mix together evenly, resulting in a more uniform dough. If you've forgotten the cookies will still work though!
Overmixing the dough can lead to tough, dense cookies. Mix just until the ingredients are combined, and then stop.
If you have one, using a cookie scoop helps to ensure that your cookies are all the same size, which helps them bake evenly.
Before baking, use the bottom of a glass, a fork, or the heel of your palm, to flatten each cookie slightly. This helps them bake more evenly and gives them a uniform shape.
Chocolate chip condensed milk cookies can go from perfectly baked to overdone very quickly, so keep a close eye on them while they're in the oven. They're done when the edges are golden brown and the centers are set.