Put raisins in a bowl and pour in enough water to cover; set aside until raisins begin to plump, at least 15 minutes.
Dissolve yeast in warm water in a bowl. Let stand until the yeast softens and begins to form a creamy foam, about 5 minutes.
Heat milk and 1/2 cup butter together in a saucepan over medium-high heat until milk is heated just below boiling, about 5 minutes. Remove saucepan from heat and cool scalded milk to lukewarm temperature.
Beat 1 cup sugar, eggs, salt, nutmeg, and vanilla extract together in a bowl; add milk mixture and yeast mixture and stir until just combined. Drain raisins and stir into sugar mixture. Beat flour, 2 cups at a time, into sugar mixture, beating well after each addition until dough is well mixed. Set bowl in a warm area of the kitchen, cover with a clean towel, and allow dough to double in size, about 2 hours.
Grease two 9×5-inch loaf pans.
Beat dough down to release air and pour into the prepared loaf pans.
Mix 1 cup sugar, 1 cup flour, and 1 tablespoon butter together in a bowl using 2 knives in a scissor-like fashion until crumbly; sprinkle over dough. Allow dough to double in size, 30 to 45 minutes.
Preheat oven to 310 degrees F (154 degrees C).
Bake in the preheated oven until a toothpick inserted in the center of a loaf comes out clean, about 45 minutes. Remove loaves from pans and cool on a wire rack.