In a large bowl, mix the flour, baking soda, and salt with the help of a whisk.

Then, in a stand mixer fitted with a paddle attachment, add butter, sugar, and brown sugar. Pulse them until they form a creamy mixture.

After that, add the dry pudding mix into the mixer along with the eggs and the additional egg yolk. Also, drop in some butter and vanilla extract and give everything a good mix.

When all of that is combined well, add in the flour mixture to it along with some toffee bits and mix until a dough begins to take shape.

After that, shape the cookie dough into a round bowl and wrap it with plastic foil. Refrigerate the dough for about 2 hours.

Then, take it out and let it soften. Use a cookie scoop to take out small scoops from the dough.

Shape them into round balls using your hands and place them on a non-stick baking tray. Place the baking tray in the oven and bake the cookies at 350℉ for about 10-15 minutes.

Then, take them out and allow them to cool down completely. Your delicious butterbeer cookies are ready!