Preheat the oven to 350°F. Line baking sheets
with parchment paper.
In the bowl of a stand mixer fitted with a
paddle attachment, beat oil and sugars at medium speed until light and fluffy,
about 3 minutes. Scrape bowl before adding vanilla extract and egg, beating
well to combine.
In a separate bowl, whisk together flour,
cocoa, cornstarch, salt, baking soda and baking powder. Gradually add the dry
ingredients to the wet ingredients and beat until a slightly sticky dough
forms. Fold in Reese's sprinkles using a rubber spatula or your hands.
Using your hands, form tablespoon-sized balls
of dough on the prepared baking sheets, spacing them at least 2 inches apart.
Sprinkle the cookie dough balls with extra Reese's and small candy eyes. Bake
for approximately 12 minutes, until puffed but still soft, taking care not to
overcook. Cool on the baking sheet for 5 minutes before removing to a wire rack
to cool completely. Sprinkle with fleur de sel and enjoy.