Preheat oven to 350 degrees.
Place parchment paper on top of baking sheets, set aside or place on ungreased baking sheets.
Add butter to a microwave dish and microwave for 25 seconds or more until butter is partially melted, like ½ of the butter should appear melted while the other half still looks like a melted butter stick.
Add the brown sugar and white sugar to a large mixing bowl with the partially melted butter and stir well to combine.
Then, beat in the egg and vanilla until just combined.
Add in the flour, baking soda, and salt and mix until just combined.
Add in the candies by hand, saving a few to press onto the tops of the cookie dough, if you wish.
Use a large cookie scoop (3 tablespoons) to scoop out 12 cookies or use a medium sized cookie scoop (1 ½ tablespoons) for 18-20 cookies and arrange them evenly on baking sheet .
Bake for 10 minutes for medium sized cookies and 13-15 minutes for larger cookies. Cookies will still be slightly underdone when you remove them from the oven. Make sure not to overbake for soft and chewy cookies. Cookies will not spread much while baking.
Let sit on baking sheet for 5 minutes before eating. Allow cookies to cool completely before storing in an air-tight container for up to 4-5 days.