In a large mixing bowl, stir together 1 3/4 cup of all-purpose flour and the yeast. In a medium saucepan heat and stir milk, sugar, butter, and salt just until warm (about 110-degrees Fahrenheit). Add milk mixture to dry mixture along with the eggs and egg yolk. Beat with an electric mixer on low for 30 seconds, scraping down the sides. Beat on high for 3 minutes. Using a wooden spoon, stir in as much of the remaining 1/2 cup all-purpose flour and the 1 cup of whole wheat flour as you can.

Turn the dough out onto a lightly floured counter. Knead in enough of the remaining flour to make a moderately soft dough that is smooth and elastic (3 – 5 minutes total). Shape the dough into a ball. Place dough in a lightly greased bowl, turning once to grease the top. Cover; let rise in a warm place till double in size (about 1 hour).

Gently deflate/punch the dough down. Divide the dough in half. Refrigerate or freeze one half of dough. Place the other dough ball into a greased 9.5-inch glass pie plate and let rest for 10 minutes. Then gently stretch it to fit the plate, molding it up the sides of the plate into a ‘pie crust.’ (It won’t be a beautiful crust, and it may not even go up the sides very well; that’s okay.) Cover and let rise for 30 minutes.

Meanwhile, for the filling, in a medium saucepan, lightly beat eggs with a fork. Stir in sugar, flour, and nutmeg. Gradually stir in milk. Cook over medium heat for about 4 minutes until the sugar is dissolved and mixture is hot (about 140-degrees F), stir in peaches and cook for about 2 minutes more to warm peaches. Stir in vanilla. Pour milk mixture into the prepared crust (after it’s raised 30 minutes,) it’s fine if some of the filling seeps under the crust. Bake in a 350-degree oven for 20-25 minutes until set. The very center of the kuchen will still be slightly liquid-y; this is okay as the kuchen will continue to firm from residual heat after removed from the oven. Cool completely and serve at room temperature, topped with additional freshly grated nutmeg.