For the cake:

1. Preheat oven to 325°F.
2. Prep a 13"x18" half-sheet pan by lining the pan with parchment paper, then spray down the edges with non-stick baking spray. These Nordic Pans are my favorite!
3. In a large bowl, cream together the sugar, butter, and shortening until smooth then beat in vanilla. Add eggs, one at a time, until fluffy.
4. In a separate bowl, sift together the dry ingredients (flour, baking powder, and salt). To save some time, you can also whisk it all together.
5. Add this flour mixture and the evaporated milk to the original mixture alternately. With an electric mixer, beat for 2 minutes on medium speed, then fold in the sour cream.
6. Pour the batter onto a prepared pan and spread it out evenly. Bake for 25-35 minutes, or until a toothpick inserted in the middle comes out clean (check at 25 minutes!).
7. Flip the cake out onto a cooling rack and allow it to cool, then follow the instructions below for filling and frosting.

For the cream cheese frosting:

1. First, cream the butter and Crisco in a mixing bowl. Mix on low speed for a couple of minutes until smooth and creamy. Add in the vanilla and cream cheese and mix again until very smooth.
2.  Gradually add the confectioners' sugar until it's all combined. It will be very stiff! Then begin adding milk until you reach the desired consistency for decorating (2 tablespoons works well for me!)

Filling and frosting the petit fours:

2. Flip the cooled cake out onto a work surface on another piece of parchment paper.
3. Torte the cake into two thin layers. This is a fancy way of saying split the cake into two layers with a cake leveling tool or sharp serrated knife.
4. With the cake bottom-up on parchment paper, lift the top layer onto another sheet of parchment paper. I've found the easiest way to do this is by sliding a flexible cutting board into the cut, then simply lifting it off.
5. If you're using a filling, such as raspberry or lemon curd, spread a thin layer onto the cut side of the cake.
6. Then spread a thin layer of frosting. I use both filling and frosting, but you could use frosting only if you don't want to use a fruit filling.
7. Using the flexible cutting board again, place the top layer of cake over the filling and/or frosting layer, lining up the edges.
8. Finally, the last step before freezing the cake is to put another layer of frosting on top. I use this as an opportunity to level out any low spots and make a really smooth, clean surface for the poured frosting! This layer of frosting can be as thin or thick as you like, so long as it's level and smooth. Why? Because the poured icing on top will only be as smooth as the surface it's poured over!
9. Once you have that top layer of frosting smooth, cut off the edges so you'll have really nice squares. Plus, you get to eat the edges and I have to tell you - they're much fought over in this house!
10. Freeze the cake. I lift it (with the parchment underneath), put it back on the sheet pan I baked it on, put a lid on (love these with lids!!), and then I put it in the freezer for around 30 minutes to an hour.

For the petit four icing:

1. While the cake is freezing, bring a pot of water to boil, then place a larger glass bowl over it. You'll do all of this recipe in the glass bowl!! This is my "double-boiler".
2. In the glass bowl, whisk together the confectioners' sugar, water, corn syrup and extracts. 
3. Continue whisking or stirring until the mixture becomes smooth and consistent. It should be thin enough to drizzle from a spoon, but not so thin that it all runs off the cake! You can also check the temperature and when it reaches 92° F, it's good.
4. When it's ready, add in the chopped white chocolate and stir until melted. I like to turn down the heat but keep my water steaming underneath as I work to keep the icing from setting up!

Icing the petit fours:

1. When the cake comes out of the freezer, use a sharp knife to cut it into squares (1-1.25 inches square). Sometimes I just eyeball it, sometimes I use my sewing ruler and/or a straight edge to get them perfect. I've also found the smallest biscuit cutter in this set works great! Do whatever makes you happy!
2. Place them on a cooling rack.
3. Working quickly (they're easier to keep pretty and square when they're cold), move a small batch of them to the prepped cooling rack and immediately start ladling the icing over the cakes, or use a skewer to dip them.
4. Freeze the remaining cake while you work and only take out as much as you can dip before it begins to thaw (I usually do 10-12 at a time).
5. I like to use cooling racks larger than the sheet pan, so there's good space between the cooling rack and the paper beneath.
6. Whichever method you choose, when you place the dipped or coated petit fours on a cooling rack, the excess runs off and onto the paper or silicone mat below and can be re-used. Let it firm up and you can peel it off and put it back into your bowl to re-melt! No waste... which I love!!
7. If you're adding sprinkles or any decorations that need to stick, add them before the icing sets (which is quick because the cake is cold).
8. Otherwise, let them set then decorate.

And finally... ENJOY!