Whisk the butter (should be at room temperature) and add the sugars. Whisk the butter sugar mix until it is creamy
Then add the egg, egg yolk and vanilla extract into the above and whisk it well.
Meanwhile sieve the flour, salt, and baking soda together. Add this flour mix into the butter mix, beat it until it all combines to form a dough. Chill the dough for few minutes, if the dough is soft.
Now line a baking tray with a baking paper, scoop small amounts of the cookie dough onto the baking tray , giving enough space between the 2 raw cookies .
Now gently press the m&m's onto each cookie with no space between the gems. (The cookies will expand whilst they ate getting baked so the space will be created between the gems).
Bake these cookies in a preheated oven at 175-180 ℃ for about 14-17 minutes or until th sides turn golden brown.
Let the cookies get cooler and then Serve.