1. Line 60 small muffin cups (1-3/4 inches in diameter) with paper or foil baking cups.
2. Beat butter, sugar, water and vanilla in large bowl on medium speed of mixer until well blended. Add eggs; beat well. Stir together 1-1/2 cups flour, salt and baking soda. Gradually add to sugar mixture, beating on low speed just until blended. Split dough in half; add remaining 1/4 cup flour to one half and cocoa to the other half, blending each thoroughly. Refrigerate doughs until firm enough to handle.
3. Heat oven to 350°F. Shape dough into 1-inch balls; place in prepared muffin cups. Bake 11 to 13 minutes or until cookie surface is set. (Vanilla cookie should be light golden.) Cookies will appear soft and moist. Do not overbake. Cool about 3 minutes on wire rack. Push peanut butter cups into center of each cookie (Peanut butter cups will soften and melt.). Cool completely in pan on wire rack.
4. Before peanut butter cup hardens again place peanut halves on surface. 60 cookies.