Place the peaches into a large heavy bottomed saucepan. Add the peach schnapps or peach nectar, if using. Simmer for 3-5 minutes until softened and juices have been released.
Add the cornstarch, cinnamon and nutmeg. Stir until the cornstarch is dissolved and there's little to no juice left in the pan. Remove from the heat and add the almond extract. Mix well then set aside to cool to room temperature.
Preheat the oven to 350°F. Spray a 13 x 9 inch baking dish with cooking spray. Set aside.
Spread the almond slices in a single layer on a baking sheet. Toast for 3-5 minutes then remove. Cool completely.
Prepare the cake mix per the directions using the amounts called for of water, oil and eggs.
Mix 1/2 of the diced peaches into the batter. Mix well then pour into the baking dish.
Bake for 30-35 minutes or until a toothpick inserted into the cake comes back clean.
Remove from the oven and using the back of a wooden spoon or similar generously poke holes over the entire cake.
In a small mixing bowl, mix together the remaining peaches and condensed milk. Pour over the cake. Cool completely.
After cooled frost with whipped topping and garnish with toasted almonds and additional peach slices, if desired. Store leftovers chilled.
Cake mix hacks 1- Add 1 tsp of pure vanilla or almond extract to the cake batter for extra flavor. 2- Replace the amount of water called for with whole milk or buttermilk. 3- Add one extra egg to give the cake more rise.