Line an 8x8-inch baking dish with parchment paper. Set aside.
Into a large mixing bowl, add the butter, granulated sugar, and brown sugar. Use a hand mixer on medium speed to cream together the butter and sugars together.
Add the peanut butter and continue mixing until fully incorporated and consistency is smooth.
Add the all-purpose flour, vanilla extract, salt, and oats. Mix just until combined.
Stir in 1/2 cup of chocolate candies.
Press the cookie dough mixture into the prepared baking dish. Set aside.
In a microwave-safe bowl, combine the chocolate chips and heavy cream. Use the microwave to heat the chocolate in 20-second intervals, stirring after each interval until the chocolate is melted and its consistency is smooth.
Pour the melted chocolate over the top of the cookie dough mixture, using a spatula to spread the chocolate so that it covers the entire surface.
Sprinkle with the remaining 1/4 cup of chocolate candies.
Cover and refrigerate until set, at least 2 hours, then cut into squares and serve.