Preheat your oven to 350°F (175°C) and position the rack in the center.

In a bowl, toss the flour, chilled cubed butter, powdered sugar, and salt together; rub or pulse until the mixture resembles coarse crumbs.

Add cold water, one tablespoon at a time, mixing until the dough just holds together when pressed — stop before it becomes sticky.

Lightly flour a surface, roll the dough to about 1/8-inch thickness, and cut circles with a cookie cutter or glass slightly larger than your mini pie pans.

Gently press each dough circle into the mini pans, trimming excess and crimping edges as desired.

Bake the shells for 10–12 minutes until the edges turn light golden; allow them to cool in the pans.

Warm the heavy cream in a small saucepan over medium heat until steaming and just below a boil, then remove from heat and stir in the semisweet chocolate chips until smooth and glossy.

Stir in the vanilla extract and add a few drops of green food coloring, mixing until the color is even.

Pour the chocolate mixture into the cooled tart shells, filling each almost to the top.

Chill the filled pies in the refrigerator until the ganache is firm, about 1–2 hours.

Roll remaining dough, use a shamrock-shaped cookie cutter to cut decorations, bake those shards until golden, and place one on each pie before serving.