Combine whole wheat flour, undissolved yeast and salt in a large mixer bowl. Heat water, honey and butter until very warm (120° to 130°F). Beat for 2 minutes on medium speed until very smooth. Stir in enough all-purpose flour to make a soft dough. Knead on lightly floured surface until smooth and elastic, about 6 to 8 minutes. Cover; let rest 10 minutes while forming cornucopia mold.
Gently fold pizza pan into a cornucopia shape, leaving a 5-inch opening and carefully crimping the narrow end in an upward curve. Generously spray with cooking spray and place on a large baking sheet that has been sprayed with cooking spray or lined with parchment paper.
Divide dough in half. Roll each into 15 x 9-inch rectangle on lightly floured surface. Cut each rectangle into six 15 x 1-1/2 inch strips. Starting at the narrow end wind a dough strip completely around the mold, overlapping strips by 1/4 to 1/2-inch. Continue adding dough strips, gently pinching ends together. TIP: insert one hand in mold and hold up upright while wrapping and tucking dough strips with second hand. Wrap the last strip around the foil opening.
You may have a little extra dough leftover. (These can be used to make rolls. Form into 2-inch balls and placed on a greased baking sheet. Let rise about 45 minutes, until almost double in size; then bake at 350° for 12 to 15 minutes.)
Place the cornucopia on prepared baking pan. Cover and let rest 15 minutes. Dough will rise very little.
Preheat oven to 350°F. Beat egg and water together in a small bowl. Generously brush over cornucopia. Bake for 20 minutes. Brush with egg wash again. Loosely cover with foil and bake an additional 40 to 50 minutes or until cornucopia seems very dry and is a deep golden brown.
Cool 10 minutes on wire rack. Carefully remove foil mold, crushing it as necessary. Store at room temperature, lightly covered. Can be made up to 5 days in advance. (Or, make up to 1 month ahead and freeze.) To serve, fill with freshly baked rolls.