Preheat Oven to 375 F
Mix dry ingredients in a large bowl
In a small bowl, cream butter and sugar until smooth, then whisk in egg and vanilla.
Add wet ingredients to dry ingredients. Mix thoroughly with a wooden spoon.
Add the Reese's Pieces, chocolate chips, and nuts (if using) to the dough. Mix thoroughly.
Line cookie sheet with parchment paper and drop about 2TBSP of dough per cookie onto the prepared sheet. The cookies will spread a bit, so leave some space between them. You might want to also press the cookie dough down a bit to get flatter cookies.
Cook for 12-15 minutes. I cooked mine for 14 minutes and got nice, chewy cookies. If you put more than one cookie sheet in the oven at a time, you will need extra cooking time.