Don't preheat the oven quite yet because this dough is better after it's been chilled. You can bake it right away, but the cookies spread a bit more.
In a large mixing bowl, beat the butter with an electric mixer on medium speed. Beat in both sugars until well mixed. Scrape sides of bowl and beat in the egg and vanilla. When egg is blended, beat in the baking powder, baking soda, and salt.
By hand, stir in the flour. When flour is incorporated, stir in the chocolate chips, Heath Bars (if using) and toasted nuts.
Using a generously heaping tablespoon, scoop up large mounds and arrange them on a foil lined plate. Cover with plastic wrap and chill for 8 hours or overnight.
Preheat oven to 350 degrees F. Line two baking sheets with regular (as opposed to nonstick or parchment) foil.
Arrange mounds of dough about 3 inches apart on baking sheets. Press tops down slightly to level with the edges.
Bake on center rack for about 15 minute or until cookies appear set and edges have browned somewhat
Let cookies cool on baking sheet for about 4 minutes, then transfer to a wire rack to cool completely.