Preheat oven to 325°F (163°C). Spray the inside of a 7 inch round cake pan with a cooking oil spray. Use a solid one-piece cake pan (no removable bottom). Line with parchment paper. You will want to create handles along with lining the bottom and sides so that you can remove the cake easily after it is done. See notes and post for how to line the cake pan properly.
Separate egg yolks and whites. Place eggs whites into fridge until ready to use.
Add chocolate chips to a large mixing bowl. Melt either in the microwave or on the stove (using the double boiler method). I used the microwave. If using microwave, heat chocolate in 15 second intervals, stirring in between with a spatula, until chocolate is completely melted and smooth.
Add in cream cheese. Mix in the cream cheese with spatula until fully incorporated and no cream cheese streaks remain.
Add in egg yolks. Using a hand whisk, whisk in the egg yolks until no egg streaks remain and batter is smooth.
Remove egg whites from fridge. Place into a separate clean large mixing bowl. Beat at highest speed until stiff peaks form. I prefer to use a stand mixer but you can also use a hand mixer.
Add one third of the egg white mixture to your egg yolk batter. Fold it in gently with a spatula until no egg white lumps remain (it's okay if there are a few streaks of white in your batter). Make sure you scoop up batter from the very bottom of the bowl each time you fold to make sure all of the batter gets incorporated with the egg whites. Repeat with the next 1/3 and then remaining 1/3.
Pour batter into prepared baking pan. The cake will be baked in a water bath. To do this, place your cake pan into a slightly larger baking pan. I used a 9 x 9 inch baking pan. Place your cake pan into the bigger pan. Pour just enough cold tap water into the outer pan so that the water level reaches 1/2 inch. Make sure to add the water to the outer pan after you've put the cake in. If you add 1/2 inch of water before, the added weight of the cake pan and cake batter will push up your water level more than 1/2 inch. I recommend using a ruler to measure the water level. If your water level is too high, the bottom of your cake will cook too much, causing a dense bottom layer.
Place cake with water bath into your oven. Bake for 55 minutes. Turn off the oven but do not open the oven door and leave the cake in the oven for one hour. It is important to leave the cake in the oven (unopened) because this allows the cake to finish cooking and the gradual drop in temperature prevents the cake from suddenly collapsing. The cake will shrink down, but it shouldn't completely collapse. After one hour, you can remove the cake from the oven. Use the cake handles to lift the cake from the pan and transfer to a plate. Let the cake cool to room temperature. While cake can be enjoyed once cooled, the flavors won't be as pronounced and the cake won't be as sweet. See notes for more details. For best result, place cake in the fridge (uncovered) for several hours or overnight. If putting it in the fridge, let it come to room temperature before serving. If desired, dust top with powdered sugar before serving.
Notes
This cake tastes best after it is refrigerated for several hours. You can eat it after it has cooled, but the flavors won't be as pronounced, the cake is not as sweet and it has a slightly eggy flavor. This is true for all Japanese-style cheesecakes. However the milk chocolate does mask most of the eggy flavor. You can always try a small slice to see the difference. If you refrigerate the cake for several hours or overnight, the flavors of the cake become much stronger and the cake is sweeter. If you do refrigerate the cake, make sure to bring it back to room temperature (about 2 hours) before serving because the cake will be much firmer and not as fluffy and light when it is cold.
While this shortcut version tastes just like regular Japanese cheesecake, it doesn't bake up as beautifully. The cake does shrink a little more, and the surface of the cake will be slightly smaller than the bottom of the cake.
If you have a kitchen scale, I recommend weighing the chocolate chips. Different brands have different sizes for chocolate chips which can make the cup measurement inaccurate.
Lining the cake pan: Before lining the cake pan, you want to create some handles so that you can easily lift your cake out of the pan. First, grease the interior of your cake pan (I used an oil spray). Then place two long strips of parchment paper across the cake pan. Each strip should run from one side of the cake pan to the other with some overhang and should overlap and form an "X" at the bottom of your cake pan. See photo in post for reference. Then, line the cake pan as you normally would (bottom round parchment paper and parchment paper for the sides). You'll want to either regrease the cake pan after adding the handles or grease the bottom round and side parchment strips so that they stick to the cake pan.
This cake is best made in a solid one-piece round cake pan that does not have a removable bottom. A springform cake pan or a cake pan with a removable bottom results in the bottom layer of the cake cooking too fast, which will produce a dense bottom layer.
I used US standard large eggs. You should have approximately 142 grams of egg whites and 75 grams of egg yolks.
Measurements are using US measurements.
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The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.