Line a baking sheet with a silicone baking sheet or parchment paper.
In a bowl, whisk together the flour and baking soda.
Set aside.
In the bowl of a heavy-duty mixer fitted with the paddle, combine the butter, brown sugar, and granulated sugar and cream on medium speed until light and fluffy.
Add the salt, vanilla extract, and egg and stir to combine.
Add the flour mixture to the butter mixture and mix on low speed until just combined.
Add the semisweet, white, and milk chocolates and chopped pecans.
Make balls of dough using a 1-ounce ice cream scoop or with your hands shape the dough into balls about the size of a gumball; place 6 dough balls on the prepared baking sheet, about 3 inches apart.
Using the palm of your hand, flatten each cookie slightly.
Press a pecan half into the center of each.
Bake until the cookies are just brown around the edges, 13 to 14 minutes.
Using an offset spatula, transfer the cookies to a rack to cool.
Repeat with the remaining cookie dough and pecan halves.
Store the cookies in an airtight container for up to 1 week.
(Dont worry, they wont last that long!)
For quick-frozen cookie dough: scoop out or roll individual balls of cookie dough and place them on a rimmed baking sheet lined with a silicone baking sheet, parchment paper, or waxed paper.
Place the baking sheet in the freezer until the dough balls are completely frozen, 1 to 2 hours.
Once they are frozen solid, transfer them to a freezable airtight container or bag for storage.
There is no need to thaw them before bakingjust increase the baking time by a minute or two.