In small saucepan, heat chocolate squares over low heat until melted, stirring constantly. Or, place chocolate squares in a microwave-safe bowl and microwave 20 seconds at a time until melted, stirring often.
Mix together flour, baking powder and salt.
In a large bowl beat butter and granulated sugar with electric mixer until fluffy. Beat in eggs until mixture is pale yellow, then add vanilla and chocolate until blended. Gradually add flour mixture, mixing just to blend.
Refrigerate dough about 1 hour.
Heat oven to 350 degrees. Shape heaping teaspoonfuls dough into 1 1/4-inch balls. Roll in confectioner's sugar.
Place 1 1/2 inches apart on greased cookie sheets. Bake 8 minutes.
Remove from oven. Firmly press chocolate kiss into center of cookie. Return to oven and bake 3 to 4 minutes. Do not overbake. Cookies are soft when hot but firm and chewy when cool.
Remove to rack to cool.
To freeze, cool cookies completely, several hours to overnight. Package in zipper food storage bags in a single layer. Freeze for up to 4 weeks.