1½ c. cold water
½ c. white sugar
¼ c. unsweetened cocoa powder
2 Tbsp. all-purpose flour
1 tsp. ground cinnamon
¼ tsp. ground cloves
¼ tsp. salt
6 c. whole milk
1 Tbsp.  vanilla

Whisk water, sugar, cocoa powder, flour, cinnamon, cloves and salt in a saucepan until smooth. Place over low heat; bring to a simmer, whisking constantly, until mixture is thickened and hot, about 4 minutes. Stir in milk; heat until hot chocolate just forms bubbles around the edge. Mix vanilla into hot chocolate. If desired, blend with an immersion blender for a frothy finish.