In a medium bowl sift together flour, baking soda and salt. Set aside.
Place the melted butter in a large bowl and whisk in granulated sugar, brown sugar and pudding mix. Whisk in the egg and vanilla extract. Add flour mixture and mix just until combined. Do not over mix. Fold in chocolate chips.
Chill the dough for at least 30 minutes (or up to 3 days). You can skip this step if you want.
Preheat oven to 175C/350F degrees. Line pans with parchment paper.
If the cookie dough is hard to handle, leave it on the counter for a few minutes.
Drop rounded balls of dough onto prepared baking sheet using heaping tablespoons or a medium (about 1.5-tablespoons) ice cream scoop, leaving about 2-3 inches (5-8 cm) between each cookie.
Bake for about 8-10 minutes, until cookies just begin to brown at the edges. Cookies will appear undone but will continue to bake on the warm baking sheet. Leave to cool for 10 minutes, then transfer to a wire rack to cool completely.
Store cookies in an airtight container for up to 3 days. Cookies can also be frozen for up to a month.