Preheat the oven to 325 degrees. Then, lightly coat the bottom and sides of an 8x8 baking dish with coconut oil. Place a piece of parchment paper on the bottom of the pan.
Melt the semi-sweet chocolate in the olive oil in a small saucepan over medium heat until creamy, stirring continuously to prevent burning. Set aside.
Whisk the cocoa powder, flour, and salt in a medium bowl.
Beat the eggs, brown sugar, white sugar, and vanilla in a large bowl until combined.
Mix the dry ingredients, egg mixture, and chocolate mixture with a spatula until just combined.
Add the chopped chocolate and gently fold two to three times with a spatula to distribute the chocolate.
Pour half the batter into the pan, spreading it into an even layer. Add the white chocolate Reese's cups, making an even layer and pressing the cups down until only the tops show.
Bake the brownies for 34 to 40 minutes until a toothpick inserted comes out with a few moist crubms.
Cool the brownies in the baking dish for an hour, then transfer them to a wire rack to cool completly.
Slice and enjoy!
Notes
Storage
Store at room temperature for up to 3 days in an airtight container.
Wrap brownies in plastic wrap and freeze for up to a month in an airtight, freezer-safe container.
Bring to room temperature before serving.
Tips
Mix the batter until just combined to ensure the brownies have the best texture.
Cool the chocolate and olive oil mixture a little before adding it to the batter to ensure it doesn't scramble the eggs.
Press your Reese's Cups down just a bit when you add them to the pan to be sure the batter completely covers their tops.