Place oven racks in top and bottom thirds of oven. Preheat oven to 325F (160C). Lightly spray 2 baking sheets or line with parchment. In a small bowl, stir flour with cocoa, baking powder and salt.
In a large bowl, using an electric mixer, beat butter with 1/2 cup (125 mL) icing sugar until creamy, about 2 minutes. Beat in egg and vanilla until mixed. It’s OK if batter separates; it will come together once you add flour. Gradually beat in flour mixture until evenly mixed. Stir in chocolate chips and nuts. Dough will be soft.
Pinch off about 1 tbsp (15 mL) dough and roll into a ball. Place on baking sheet. Continue with remaining dough, placing balls about 2 inches (5 cm) apart. Using the palm of your hand, flatten balls slightly. Bake on 2 racks in preheated oven, switching position of sheets halfway through baking, until cookies are set, 10 to 14 minutes.
Remove cookies to a cooling rack. Repeat with remaining dough. When cool, refrigerate cookies up to 1 week or freeze up to 1 month. Just before serving, roll cookies in icing sugar to evenly coat.
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Nutrition (per serving)
They look like mini snowballs, but taste like a cross between nutty brownies and buttery shortbread. Yum!