Soak the raisins in very hot but not boiling water for 10-15 minutes, drain and let cool completely.
Preheat the oven to 400F and line a baking sheet with parchment paper and set aside.
In a small bowl, mix together 2 tablespoons of sugar with the cinnamon and set aside.
In a large bowl, mix together flour, remaining sugar, salt and baking powder until well combined.
Grate the frozen butter into the flour using the large holes of a box grater.
Using your hands or a fork and working quickly, work the butter into the flour until just combined; do not overmix.
Add the cooled raisins into the bowl and stir until just combined and evenly distributed.
Stream in the heavy cream and use a fork to evenly distribute the liquid.
As soon as shaggy dough starts to form, turn out the dough onto a lightly floured work surface.
Gently knead the dough until it just comes together and shape it into a 1 inch thick square.
Using a bench scraper or very sharp knife, cut the dough into 4 equal pieces.
Generously sprinkle 3 of the 4 dough pieces with the cinnamon sugar mixture, then stack them on top of each other, making sure the piece with no cinnamon sugar is at the top.
Use a rolling pin to gently compress the dough stack, then roll the dough into a ¾ to 1 inch thick rectangle (if the dough starts to stick add a light dusting of flour).
Lightly flour the sharp end of 3-4 inch round cookie or dough cutter and punch out as many biscuits as possible, then transfer to the prepared baking sheet.
Reroll the dough scraps and punch out more biscuits until the dough can’t be rerolled.
Transfer the biscuits to the freezer and let the butter firm up for 10 minutes, then brush the biscuit tops with heavy cream and lightly sprinkle with the cinnamon sugar mixture.
Bake for 15-20 minutes, or until the tops are golden brown and transfer to a wire rack to cool for 5 minutes.
While the biscuits are baking make the glaze.
In a small bowl combine the powdered sugar, milk and vanilla extract and mix until well combined and smooth; if the glaze is too thick add 1 tablespoon of milk at a time until you’ve reached the desired consistency.
Drizzle over the warm biscuits and enjoy!