Preheat the oven to 350°F (175°C) and line baking sheets with parchment paper.

In a medium bowl, whisk together the flour, salt, baking soda, and cream of tartar.

In a large mixing bowl, beat the butter with granulated and powdered sugars until fluffy. Add oil, vanilla, and peppermint extract.

Incorporate the eggs one at a time, mixing until fully merged.

Gradually add the flour mixture to the wet ingredients and fold in the sprinkles.

Roll the dough into 2-inch balls and place them on the baking sheets. Flatten each ball slightly with a sugared glass.

Bake for 8 minutes until slightly underdone. Cool on a wire rack.

Heat the heavy cream in a saucepan until simmering, then pour it over the dark chocolate. Stir until smooth.

Spread ganache over each cooled cookie and top with peppermint bark squares. Let sit until set.