Make a lengthwise slit in each date. Squeeze the date open and remove the pit. Knead the marzipan to soften it. Take 1 Tbsp. of the marzipan and shape it into an oblong ball. Stuff the marzipan into the centre of a date. Gently squeeze the date shut, leaving some of the marzipan still exposed. Repeat with remaining dates.
Melt the chocolate in a small bowl set over simmering water. Line a baking sheet with parchment paper. Dip one of the stuffed dates halfway into the melted chocolate. Set on the baking sheet, stuffed side up. Sprinkle the dipped side of the date with a few crushed pistachios. Repeat with remaining dates. Refrigerate the dates to set the chocolate. Keep the dates refrigerated until ready to serve.
Note: Medjool dates are available in the produce department. Marzipan and Belgian chocolate are available in the bakery. Shelled pistachios are available in bulk foods.