In a small pan, warm milk (120-130). Take out ¼ cup of milk and place in a large bowl or 2 cup measuring cup, add in 1 tbsp sugar and the yeast packs. Let it sit for 5–10 minutes until foamy.
Melt the butter. Let cool slightly. In a small bowl, beat egg and vanilla extract.
In a large bowl, mix flour, sugar, salt, and cinnamon. Add nutmeg and allspice if using.
Pour in the yeast, butter, egg-vanilla and mix until a dough forms. Add in raisins or currants and knead for 8–10 minutes, until smooth and elastic. Form dough into a large ball and place in a greased bowl.
Cover the dough with a clean cloth and let it rise in a warm place for 1 to 1.5 hours, or until doubled in size.
Once your dough has risen, punch it down and divide it into 12 even pieces. Roll each piece into a smooth ball and place on a parchment-lined baking sheet, spaced slightly apart. Cover and let them rise again for 30–45 minutes, until puffy.
Optional step: once the buns have risen, you can use a very sharp knife to cut a cross on the top of each bun. The grooves act as a channel for the glaze. It's up to you whether you want to bother with this step.
Preheat your oven to 375°F (190°C). Mix one egg with a splash of milk and brush over the top of the buns. Bake for 20–25 minutes, until golden brown on top. Remove from the oven and allow them to cool completely.
For the glaze: Mix 1 cup of powdered sugar, 1-2 tbsp of milk (as needed) and 1/2 tsp vanilla. Icing should be thick. Add the icing to a small plastic bag and snip the corner. Make a cross on each roll with the icing. However, if you want to eat them warm and right from the oven just glaze immediately after baking. The icing will melt into the buns and given them a beautiful glossy finish.
Serve and enjoy!
Store leftovers in an airtight container for up to 3 days. To freeze, wrap individually and place in a freezer bag for up to 3 months.