1/2 cup butter or margarine
Cream together butter and sugars until light and fluffy. Beat in egg and peanut butter. Blend in vanilla.
Sift together flour, baking soda and salt. Gradually add dry ingredients to creamed mixture; blending well. Shape dough in 1-inch balls. Place balls about 2-inches apart on greased baking sheets. Flatten with floured tines of fork.
Bake at 375 degrees 8 to 10 minutes or until golden brown. Remove from sheets; cool on racks.