Heat the milk, in the microwave or a saucepan, until it is "fingervarm" (finger warm), meaning it should feel warm to the touch but not hot. Add your active dry yeast/fresh yeast and 1 tbsp of sugar, stir, and leave it for 5-10 minutes until the mixture starts to bubble up, meaning your yeast is alive and not expired. If using instant yeast, you do not need to do this step; you can add the yeast directly to the mixing bowl with everything else.
Add the remaining sugar (2tbsp), egg, orange zest, salt, and cardamom to a large bowl/bowl of a stand mixer and mix well. Once the yeast mixture has bubbled up a bit, add it to the egg mixture. Mix together.
Add the flour and softened butter, mixing with a wooden spoon or the dough hook on a stand mixer until the dough starts to come together.
Knead until smooth and elastic, about 10 minutes. Use a stand mixer if you would prefer! Add more flour if the dough is too sticky – if it sticks to the sides of the bowl or is really sticking to your hands, you need a little bit more flour! It is okay if it's a little bit sticky, as it makes for super soft buns, but it shouldn't be impossible to knead or work with.
Add the candied orange and white chocolate at the end of the kneading period, making sure it's well distributed. You may need to do this by hand even if using the stand mixer.
Cover the dough with cling film or a clean dishtowel and let rise at room temperature (if room temp is very cold wherever you are, put it in a warm place, i.e. under a light) for about an hour or until doubled in size.
Once your dough has doubled in size, shape it into 15 balls. Pinch the dough together so you have a smooth ball of dough, then roll each ball on an unfloured surface to close any seam/imperfections on the bun.
Place the buns close together, almost touching, in a 3x5 grid on a parchment lined baking sheet (we used a "half sheet" baking pan size).
Cover and let rise until puffed up and touching, about 30-45 minutes more in a warm place.
Towards the end of the rising time, preheat oven to 375F (190C).
Mix together flour and water for the topping. Add to a piping bag or a small plastic bag. You can also use a parchment paper cone for piping. Pipe lines vertically and horizontally across the buns, creating the cross shape where the lines overlap on the buns.
Bake for 15-20 minutes, until the tops are golden brown and baked through in the center.
Brush syrup/honey/marmalade on the top while they are still warm for a nice shiny top.