Best-Ever Hot Cross Buns

In a medium bowl, combine milk, yeast, and a pinch of sugar. Let sit, without stirring, until foamy, about 20 minutes. Whisk butter, egg yolk and vanilla into the yeast mixture. In a large bowl, whisk together the flour, remaining sugar, salt, cinnamon and nutmeg. Make a well in the center of the flour mixture and add the yeast mixture. Stir with a wooden spoon until the mixture is a thick, shaggy dough. Stir in currants. Turn the dough onto a heavily floured surface and knead until the dough is soft and elastic, 8 to 10 minutes. Shape the dough into a large ball. Grease the inside of a large bowl with butter and put the dough in the bowl. Cover with plastic wrap and let rise at room temperature until doubled in size, about 1½ hours. When the dough is ready to form into rolls, butter a 9”-x-13” baking pan. Turn the dough onto a lightly floured surface and pat it into a large rectangle. Divide the dough into 12 portions with a sharp knife or pizza wheel. Shape each piece into a roll, tucking the edges under, and place each roll seam side-down into the butter pan. Cover with plastic wrap and let rise in a warm place until the rolls have doubled in size, about 45 minutes. After the second rise, preheat oven to 375°. Brush tops of buns with egg wash. Bake until golden and puffy, 22 to 25 minutes. Make glaze: Whisk together powdered sugar, milk, and lemon zest until smooth. Transfer to a medium resealable plastic bag and make a small cut in the corner of the bag. Pipe a thick cross shape over each bun. Serve warm or at room temperature.