Preheat the oven to 375°F (190°C). Line two baking sheets with parchment paper.
For the chocolate chip cookies: In a medium bowl, whisk together 2 1/4 cups flour, baking soda, and salt. Set aside.
In a large bowl, beat the softened butter, granulated sugar, brown sugar, and vanilla extract with an electric mixer on medium speed until creamy, about 2 minutes.
Add eggs one at a time, beating well after each addition.
Gradually beat in the flour mixture until just combined.
Stir in the chocolate chips with a spatula.
Drop rounded tablespoons of dough onto the prepared baking sheets, spacing about 2 inches apart.
Bake the chocolate chip cookies for 9 to 11 minutes or until golden brown around the edges but still soft in the center.
Remove from oven and let cookies cool on the baking sheet for 2 minutes before transferring to a wire rack to cool completely.
For the sugar cookies: In a medium bowl, whisk together 2 3/4 cups flour, baking powder, and salt. Set aside.
In a large bowl, beat the softened butter and granulated sugar with an electric mixer on medium speed until light and fluffy, about 3 minutes.
Add the egg, vanilla extract, and milk, beating until combined.
Gradually add the flour mixture, mixing on low speed until just combined.
Roll the dough into 1-inch balls and place them 2 inches apart on the prepared baking sheets.
Flatten each ball slightly with the bottom of a glass dipped in sugar to prevent sticking.
Bake the sugar cookies for 10 to 12 minutes or until the edges are lightly golden.
Remove from oven and allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.