In a large bowl, beat butter, peanut butter, granulated sugar, and brown sugar until creamy.
1/2 cup salted butter, 1/2 cup creamy peanut butter, 1/2 cup (100g) granulated sugar, 1/2 cup (100g) brown sugar
Add egg and beat until combined. Scrape bottom and sides of bowl.
1 large egg
Add flour, baking soda, baking powder, and salt. Mix until combined. Set aside.
1 1/2 cups (212g) all-purpose flour, 1/2 teaspoon baking powder, 1/2 teaspoon baking soda, 1/2 teaspoon salt
In a microwave-safe bowl, combine chocolate chips, sweetened condensed milk, and butter. Melt for 60-90 seconds, stopping every 30 seconds to stir until smooth.
1 cup semisweet chocolate chips, 1/2 cup sweetened condensed milk, 1 Tablespoon salted butter
Roll out cookie dough 1/4-inch thick between two large pieces of plastic wrap or waxed paper. Remove the top layer of plastic wrap and spread melted chocolate on dough in an even layer.
Use plastic wrap or waxed paper to roll cookie dough into a tight log from the long side. Wrap tightly and chill in the fridge for 30-45 minutes.
Preheat the oven to 375°F. Line two baking sheets with parchment paper.
Once dough has chilled, unwrap and slice into 1/4-inch discs using a serrated knife. Arrange on a baking sheet spaced 2-3 inches apart.
Bake for 10-12 minutes until lightly browned around edges. Cool on a wire rack.