Adjust rack to center of oven; preheat oven to 375 degrees F. Butter a baking sheet (including the sides) at least 15-½ by 10-½ inches. Trace two circles, each 6 inches in diameter, in opposite corners of the baking sheet, taking care to leave at least 1 inch between the edge of the baking sheet and any part of a circle. In food processor fitted with steel blade, combine flour, sugar, cocoa powder, baking powder, and salt. At high speed, process until well mixed, about 15 to 20 seconds. Add butter pats; process until mixture forms fine crumbs, about 30 seconds. Turn mixture into large bowl. Stir in chips and nuts until evenly distributed. Gradually beat ⅔ cup heavy cream into the egg, beating well with fork to combine. All at once, add to dry ingredients. With large spoon, stir to mix. All of the dry ingredients will not be incorporated. Lightly flour your hand; with the mixture still in the bowl, knead it gently, just until it is all gathered into one mass. You may have to make a judgment call here, as sometimes this dough requires another tablespoon or two of cream before it will hold together. The dough should be slightly sticky, but stiff enough to hold its shape. (If you wish, you can turn the mixture out onto a lightly floured board, and knead it on that.) Do not handle the dough more than necessary. Divide dough into two equal portions; flatten each portion into a rough circle, then place inside one of the circles traced on the baking sheet. With lightly floured hands, pat each portion out until it fills the traced circle. The edges may be a bit rough in shape, but the thickness of the dough should be as even as possible. With a lightly floured finger, poke a hole in the center of each circle, and widen the hole to about ¾-inch diameter. Lightly flour a sharp knife. Score each circle into eight wedges, re-flouring the knife lightly as necessary. Bake the scone circles 15 to 20 minutes, turning the sheet back-to-front once about halfway through baking time. The hole in the middle of each circle will partially fill in during baking. When done, a toothpick inserted about an inch from the center of a circle will emerge with a few moist crumbs still clinging to it. Do not overbake! Remove baking sheet to cooling rack. Allow baked scones to stand 2 minutes before cutting. To cut, use a small, sharp, serrated knife to saw gently through the score marks in each circle (I find it best to cut from the outer edge inward). You’ll have to rinse and dry the knife blade frequently to keep the cuts neat. Remove scones to cooling rack with broad-bladed metal spatula to cool slightly. Serve warm, or cool completely before storing or freezing.