In a mixing bowl, cream together sugars, butter, and vegetable oil until smooth and creamy.
Add eggs to the mixture one at a time, beating well after each addition until fluffy.
Stir in baking powder, salt, baking soda, and vanilla extract until well combined.
Gradually add all-purpose flour to the wet ingredients, mixing until a soft dough forms.
Fold in chopped M&M's (as many as desired) into the cookie dough.
Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper or grease it lightly.
Roll the cookie dough into balls and place them on the prepared baking sheet, spacing them apart.
Gently press 5 whole M&M's onto the top of each cookie dough ball for decoration.
Bake in the preheated oven for 7-8 minutes or until the edges are lightly golden.
Remove from the oven and allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.
