Dulce de Leche Icing
1 fourteen-ounce can sweetened condensed milk
1 cup pecan halves
3 sticks unsalted butter, softened
4 cups powdered sugar
3 tablespoons heavy cream
1 teaspoon vanilla
Make dulce de leche: Remove label from can and punch two small holes at opposite sides of lid. Set can in a saucepan, add water to cover two thirds of can, and simmer for 2 hours, maintaining water level. Open carefully while still hot, spoon into a bowl, and let cool.
Preheat oven to 350 degrees. Toast pecans for 6 to 7 minutes; reserve for decorating cake. Using an electric mixer, beat butter until fluffy, 3 to 4 minutes. Beat in powdered sugar, then cream, vanilla, and dulce de leche, mixing until fluffy, about 2 minutes.
Peach Filling
1 cup chopped pecans, toasted (see directions above)
1 ten-ounce jar peach preserves
1 1/4 cups chopped peaches, fresh or well-drained frozen
Allow toasted pecans to cool, then mix with preserves and peaches.
Cake
3 cups cake flour
1 1/4 teaspoons baking soda
1/4 teaspoon salt
3 sticks unsalted butter, softened
3 cups sugar
6 large eggs
8 ounces sour cream
2 teaspoons vanilla
1 cup coarsely chopped pecans, toasted (see directions above)
1 cup chopped peaches, fresh or well-drained frozen
Line bottoms of three 9-inch cake pans with parchment or waxed paper and grease sides and paper. Combine flour, baking soda, and salt and set aside. Using an electric mixer at medium-high speed, cream butter and sugar until fluffy, 2 to 3 minutes. Mix in eggs one at a time, then sour cream and vanilla. Beat in flour mixture on low speed until just incorporated. Fold in pecans and peaches by hand. Pour batter into pans and bake until light brown, 35 to 40 minutes. Let cool in pans for 15 minutes. Spread peach filling on one cake layer; top with a second layer and repeat, then add top layer. Ice cake, then press pecan halves around edge. Serves 10 to 12.
