Using a small paring knife, cut a slit into each Medjool date and carefully remove pits. Gently squeeze dates open and stuff a pecan half inside each.
Melt dark chocolate in the top of a double boiler, stirring frequently. Remove from heat when chocolate is almost fully melted; stir until fully melted. Be sure to keep any moisture, water or even steam away from the chocolate.
Using a fork, dip dates in chocolate and place onto a wire cooling-rack. Let cool completely.
Melt white chocolate in the top of a double broiler as directed above. Spoon into a small piping bag or a small resealable plastic bag; snip a small amount off the corner and drizzle over chocolate dipped dates. Let cool completely before serving.