Sift together the flour, baking soda, and salt.
In a mixing bowl, cream butter and sugar; add egg and beat well. Blend in peanut butter. Add flour alternately with the milk, mixing thoroughly after each addition. Add vanilla. For each cookie, shape 1 teaspoon of dough into a ball. Roll each ball in cereal. Place cookies about 2 inches apart on lightly buttered baking sheets. Bake at 350° 10 to 12 minutes.
Makes about 3 dozen peanut butter cookies.