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 9x5-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.
Keep a close watch on the coffee cake when it is cooking. It may take longer or shorter than the allotted time, depending on your oven. The reason the temperature is so low is because it tends to brown quickly if set higher.
Per Serving: 404 calories;8.4 g fat;
75 g carbohydrates;
7.9 g protein;
53 mg cholesterol;
214 mg sodium.