Step 1

Preheat oven to 400°. Toast pistachios on a rimmed baking sheet, tossing halfway through, until golden brown, about 4 minutes. Let cool; coarsely chop.

Step 2

Meanwhile, crush cinnamon stick with the side of a chef’s knife to break into pieces. Toast cinnamon, cardamom, peppercorns, and cloves in a medium skillet, stirring occasionally, until slightly darkened and very fragrant, about 4 minutes. Transfer to spice mill or mortar and pestle and let cool; finely grind.

Step 3

Grate beets on the large holes of a box grater. (You should get 4 heaping cups.) Transfer beets to a medium saucepan and add milk and butter. Cook over medium heat, stirring often, until thickened, 16–20 minutes. Stir in brown sugar, vanilla, and 4 tsp. spice mixture (use the leftover spice mixture in other desserts, hot chocolate, or to make chai). Reduce heat to low; cook, stirring, until liquid is almost completely evaporated, 15–20 minutes.

Step 4

Stir half of the pistachios into beet mixture and divide among 8 small ramekins or small bowls.

Step 5

Top halwa with remaining pistachios just before serving.Do ahead: Halwa can be made 3 days ahead. Cover and chill.