Preheat the oven to 375°F (190°C/gas mark 5). Line a cookie sheet with parchment paper.
Add the flour, baking soda and baking powder to a bowl and whisk together. Set aside.
Add the butter, brown sugar, corn syrup, salt, vanilla and butterscotch flavor to a large bowl or the bowl of a stand mixer. Beat these together until fully incorporated.
Add the egg and mix until incorporated.
Add the dry flour mixture in and gently mix together, just until it is incorporated. The dough will be very soft and sticky.
Using a cookie scoop or a tablespoon, portion the cookies out onto the baking sheet, leaving about 2" space for them to spread.
Bake the cookies for 8-10 minutes. They will not really brown much at all, but they will spread out quite a bit and the tops will be speckled with little holes.
Slide the parchment paper with the cookies off of the cookie sheet and onto a cooling rack.
Making the Glaze
In a microwave safe bowl (or a heatproof bowl if you choose to do this in a double boiler), heat the butterscotch chips and the coconut oil on 50% power for 30 seconds. Mix well afterwards and continue to heat in 10 second bursts until almost all of the chips are melted. Mix well until they all fully melt.
With the back of a spoon or with a small offset spatula, spread the glaze on top of the cookies.
These cookies keep well at room temperature for about a week.
Notes
You can also try adding the butterscotch chips as a mix-in, rather than as a glaze. Both work really well! If you want to mix it in, just fold them into the batter at the end before scooping the cookies onto the baking sheet.