Heat the oven to 180 degrees C (350 degrees F).With either a standing mixer, or a handheld mixer, cream the butter and sugar together until the mixture becomes pale and fluffy.If you don't have a mixer, use your very strong arm to beat them with a wooden spoon.
Sift the flour, baking powder, and salt into the bowl with the creamed butter-sugar mixture.
Use a wooden spoon or a silicone spatula to mix everything together until you get a homogeneous mixture.
Add the chocolate chunks, and chopped nuts if using. Mix them in gently. I find that it is better to use your hands at this stage to mix the chocolate chunks in uniformly.
Line a cookie sheet with baking paper.Use a teaspoon, or your hands, to take walnut-sized pieces off the dough.Roll each lump into a ball and place it on the cookie sheet.Squash each ball with a fork to flatten it out.
Bake the cookies for 10 - 12 minutes until they start to turn a slightly golden-brown color. Take the cookie tray out of the oven and leave the cookies to cool on it for 10 minutes.Take the cookies off the tray and leave them on a wire cooling-rack to cool completely.
Notes
Pam's cookies will keep well in a sealed container for up to 5 days (though they have never lasted that long at our house. They often get eaten hot off the cookie tray!).