Soak currants and raisins in a bowl of warm water for 30 minutes. Drain and pat dry with paper towels; stir in candied peel.
Sift flour and cinnamon into a large bowl. Make a well in the center of the flour. Add yeast and sugar to the well; pour in 1/4 cup lukewarm water. Let stand until yeast begins to foam, about 5 minutes.
Stir remaining 3/4 cup lukewarm water, milk, eggs, and salt into the flour mixture until dough comes together.
Turn dough out onto a lightly floured surface. Add currant mixture; knead until evenly incorporated and dough is smooth and elastic, about 5 minutes. Transfer to a bowl and cover with a damp cloth. Let rise in a warm place until doubled, 45 minutes to 1 hour.
Grease two 9x5-inch loaf pans lightly with butter. Flatten dough gently and shape into 2 loaves. Place 1 loaf in each pan and cover with a damp cloth. Let rise in a warm place until puffy, about 45 minutes.
Preheat oven to 350 degrees F (175 degrees C).
Bake loaves in the preheated oven until firm and dark brown, about 45 minutes. Invert onto a wire rack to cool completely before slicing, about 1 hour.