Pre-heat the oven to 375°F.
Sift 3 cups flour twice. In a large bowl, mix the flour, baking powder, sugar and cocoa. Cream 1 cup butter or margarine; blend into the flour mixture. Add 1/3 cup milk, 1 teaspoon vanilla and the walnuts. Mix thoroughly with your hands until well blended. (The dough should be the consistency of pie crust, but not sticky.)
For each cookie, pinch off about 1 teaspoon dough. Using your hands, roll it into balls, each about 1 inch in diameter. Place on greased baking sheets. Do not flatten. Bake about 10 minutes, until lightly browned. Remove the cookies from the baking sheets; cool on racks.
To make the chocolate glaze, melt the chocolate squares over low heat. Cream with 1 tablespoon butter, 1 teaspoon vanilla and 2 cups confectioner’s sugar. Gradually add the hot milk, beating until smooth.
When the cookies are cool, drizzle each generously with chocolate glaze. Sprinkle with candy sprinkles, if desired.