• Adjust your oven rack to the lower position and preheat your oven to 325°F.

Make the Strawberry Sauce:

• Add the fresh or frozen strawberries to a small saucepan along with the granulated sugar. Cook and stir until the strawberries have softened and released all of their juices. Strain the liquid through a sieve and allow to cool in the fridge until needed.

Make the Angel Food Cake:

• Clean and dry all of your bowls, mixers, and spatulas well. Optional: Wipe everything with a little white vinegar or fresh lemon juice to get rid of any oil residue.
• Sift the cake flour, powdered sugar, and salt in a large bowl and set aside.
• Separate the eggs one at a time in a small bowl and add the egg whites to a large glass bowl or bowl of a stand mixer. Be careful not to get any yolk in with the egg whites.
• Add the granulated sugar and cream of tartar to the bowl with the egg whites. Place the bowl over a pot of gently simmering water. Make sure the bottom of the bowl isn't touching the water or the egg whites will start to cook.
• Whisk the mixture frequently over the simmering water until the sugar is dissolved and the temperature reaches 140°F on a digital instant read thermometer. This will take about 5 minutes. If you don't have a thermometer you can check by rubbing the mixture between your fingers to make sure there aren't any sugar granules.
• Take the bowl off of the saucepan and wipe any water off of the bottom of the bowl. Use an electric or stand mixer with a whisk attachment and begin whipping the egg whites on low speed until starting to thicken. Increase the speed to medium and keep mixing until the egg whites are thick and glossy with stiff peaks. This can take 10-15 minutes depending on the kind of mixer you're using.
• Add two tablespoons of the strained strawberry liquid and mix until just combined. 
• Fold the batter: In several additions, use a rubber spatula to gently fold the meringue into the sifted dry ingredients. After the last addition, fold until the batter is smooth with no pockets of dry ingredients remaining.
• Add the angel food cake batter to an ungreased angel food cake pan and use a spatula to spread it out evenly.
• Bake in the preheated oven for 35-40 minutes. Avoid opening the oven door during the first 35 minutes. The cake is done when the top is light golden brown and a toothpick inserted into the center comes out clean. You can also check the internal temperature with a digital thermometer, it should be at least 205°F.
• Remove the cake from the oven and immediately flip the pan upside down to cool the cake. Since the pan was ungreased the cake won't fall out, and cooling upside down helps keep it from deflating. Allow the cake to cool completely at room temperature upside down for at least 1 hour.
• When the cake is cool, remove it from the pan by running a knife around the outer edge of the cake to separate it from the sides of the pan. Run your knife along the bottom and around the center until you are able to lift the cake from the pan. Transfer to a serving plate and let cool in the fridge before adding the whipped cream frosting.  

Whipped Cream Frosting:

• Use an electric mixer to beat the cold mascarpone cheese or whipped cream cheese spread until smooth.
• Add the cold heavy whipping cream and mix until starting to thicken. Add the powdered sugar and mix until thick and billowy, be careful not to over whip the cream.

Assemble:

• Once the cake has cooled completely, use a large serrated knife to slice it in half horizontally. Arrange some sliced strawberries on top of the cake, and pipe or spread the whipped cream frosting on top. Gently set the cut cake layer on top and decorate with more sliced strawberries and more whipped cream.