Put flour, granulated sugar (not coarse sugar), baking powder, salt, and cinnamon (if using) in a large food processor and gently pulse to combine and fluff. Then, pull the wet ingredient mixture and unsalted butter from the fridge. Cut the butter into cubes and add it to the food processor along with the wet ingredient mixture. Pulse the food processor just 10-15 times to combine the ingredients. Do not overmix. Dough should be crumbly with lentil-size pieces of butter running throughout. Finally, add the cinnamon chips or chocolate chips and pulse another 5-6 times just to distribute. (See TIP B below for alternatives to using a food processor.)
TIP A: If you've spent any time consuming food media, then you're probably familiar with the statement, "Baking is a science and cooking is an art form." Personally, I think there is art and science to both, but it's true that precision—particularly around measuring and balancing ingredients—tends to be much more critical with baking than it is with cooking. When my mom shared this recipe, she made certain to remind me that the flour should be spooned from its storage container into a measuring cup (vs. scooped directly with the measuring cup) so that it does not get compacted. Unintended compacting can result it adding too much flour which will leave your scones—or any baked good— a bit dry. I guess the devil (or in this case, the delight!) is in the details.
TIP B: I mentioned the importance of keeping your ingredients cold at the outset of this recipe, but it is particularly important with the butter. You want the butter cold enough so that it can withstand all of the processing, mixing, and dough-shaping that happens. It should still show-up as little flecks in the finished product, right before freezing and baking. These flecks of solid butter melt in the oven creating tiny air pockets that result in the scones' signature light, layered texture. You don't want to miss out on this!
TIP C: My mom swears by using a food processor for this recipe because it means that she can achieve the desired crumble of the dough quickly and without using her hands (which will naturally warm the ingredients). If you don't have a food processor, you can give the ole two-knife scissor technique a try or I recommend using a multi-blade pastry blender.