Preheat the oven to 350° F (180° C).
Using a stand mixer or an electric hand mixer, cream together the butter and sugars until light in color and fluffy in texture.
3/4 cup (167g) salted butter, softened, 3/4 cup (185g) brown sugar, 1/4 cup (58g) granulated sugar
Scrape down the sides and add in the eggs, corn syrup, vanilla and milk. Mix until thoroughly combined.
2 eggs, 1 Tbsp corn syrup, 1/2 Tbsp vanilla extract, 1 Tbsp milk
Next, add the flour, cocoa, corn starch, baking soda, and salt. Mix until your chocolate cookie dough forms. The dough will be soft.
2 cups (304g) all-purpose flour, 1/2 cup (60g) dutch processed cocoa powder, 1/2 Tbsp corn starch, 1 tsp baking soda, 1/2 tsp salt
Add in the m&m candies and peanut butter chips and mix gently just until distributed throughout the dough.
1 cup (200g) mini Valentine m&ms, plus more for topping, 1 cup (200g) peanut butter chips
Press the dough into a greased 9x13 pan. Sprinkle the top with powdered sugar.
1/3 cup (35g) powdered sugar
Bake at 350° F (180° C) for 14-16 minutes or until the dough has risen, no longer looks wet and glossy and begins to crackle.
Allow the bars to cool completely.
While the cookies are cooling, make the ganache. Measure out the heavy cream into a microwave-safe bowl.
1/3 cup (79ml) heavy cream
Microwave the cream for 1 1/2 minutes or until it is boiling.
Remove the bowl from the microwave and add in the chocolate and peanut butter chips. Use a spoon and push the chips around so they are all covered by the heavy cream.
1/2 cup (100g) chocolate chips, 1/2 cup (100g) peanut butter chips
Allow the chocolate and peanut butter chips to sit in the hot cream for 3-5 minutes.
After the time is up, use a whisk and stir the chips into the heavy cream until smooth. If some of the chips have not melted, feel free to pop into the microwave for 15 seconds.
Spread ganache onto the cookie bars and quickly top with a few whole pieces of puppy chow, some mini m&ms, and some festive sprinkles.
1 cup puppy chow, store bought or homemade, Valentine sprinkles
Allow the ganache to set completely before cutting the bars.
Store in an airtight container at room temperature for 3-5 days.