Combine the 3 tbsp brown sugar, 3 tbsp water, and 1/4 tsp cinnamon in a small saucepan over medium heat. Stir and simmer for 3 to 4 minutes until the sugar dissolves, then remove from heat and cool for 10 minutes.

Whisk together the 1/4 cup heavy cream, 2 tbsp milk, and 1 tbsp vanilla syrup for 30 to 45 seconds until slightly thickened but still pourable.

Fill 2 tall glasses with ice and divide the 2 cups cold brew between them. Add the cooled syrup and stir to combine.

Pour the sweet cream slowly over the back of a spoon to float it on top of each drink.

Dust each glass with a pinch of ground cinnamon and serve immediately with a wide straw.