Preheat the oven to 375°F (190°C). Line two baking sheets with parchment paper.
In a medium bowl, whisk together the all-purpose flour, baking soda, and salt. Set aside.
In a large bowl, beat the 1 cup softened butter, granulated sugar, and light brown sugar together until creamy and smooth, about 2-3 minutes.
Add the vanilla extract and eggs to the butter mixture and beat until well combined.
Gradually add the flour mixture to the wet ingredients, mixing until just combined.
Fold in the semisweet chocolate chips evenly.
Drop rounded tablespoons of cookie dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake for 10-12 minutes or until the edges are golden brown but the centers are still soft.
Remove from oven and let the cookies cool on the baking sheets for 5 minutes, then transfer to wire racks to cool completely.
To make the filling, beat the 1 cup softened butter until creamy.
Gradually add the powdered sugar, beating until smooth.
Add the vanilla extract and heavy cream, and beat until the filling is light and fluffy.
Once the cookies are completely cool, spread about 2 tablespoons of the buttercream filling onto the flat side of one cookie.
Top with another cookie, flat side down, and gently press to create a sandwich.
Repeat with remaining cookies and filling.
Serve immediately or refrigerate the cookie sandwiches in an airtight container for up to 3 days.