In a large bowl, beat together butter, sugars, and vanilla until well-combined and creamy. Add egg and mix well. Add flour to bowl and evenly sprinkle baking soda and salt over top. Stir until just combined. Mix in mini chocolate chips and refrigerate cookie dough for 30 minutes.
Position oven rack in center of oven and preheat to 350°F. Line a large baking sheet with parchment paper. Drop cookies by rounded tablespoons onto prepared cookie sheet, spacing at least 1 1/2 inches apart. Bake for 8 to 12 minutes or until set and light golden brown. Allow to cool on baking sheet for 5 minutes before removing to a rack and cooling completely. Store in an airtight container.
You may use an electric mixer for this recipe if you wish, but a wooden spoon works just fine.
Whole wheat pastry flour is the key to 100% whole wheat cookies that aren't heavy and dense. If you can't find WW pastry flour, you may substitute half white flour and half regular whole wheat flour...but the cookies won't turn out quite the same and they won't be 100% whole wheat.
Be sure you sprinkle the baking soda and salt over the flour rather than dumping it in one clump, to ensure even distribution. This step saves you from having to whisk the dry ingredients separately in another bowl.
You may skip refrigerating the cookie dough before baking if you're short on time. However, this step prevents the cookies from spreading too much and results in thicker, chewier cookies. The cookies will probably bake faster if the dough is not chilled, so watch the cooking time carefully.