Creating your Chocolate Cake with Strawberry Filling involves the following steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
2. Mix Dry Ingredients: In a large bowl, sift together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.
3. Combine Wet Ingredients: In another bowl, whisk together eggs, milk, oil, and vanilla extract until well combined.
4. Create Batter: Gradually add the wet mixture to the dry mixture, mixing just until combined.
5. Add Boiling Water: Carefully stir in the boiling water until the batter is smooth. It will be thin.
6. Bake the Cakes: Divide the batter evenly between the prepared pans and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
7. Cool the Cakes: Once baked, remove the cakes from the oven and let them cool in the pans for 20-30 minutes. Then transfer them to wire racks to cool completely.
8. Prepare Strawberry Filling: In a saucepan over medium heat, combine sliced strawberries, sugar, and lemon juice. Cook until the strawberries start to break down, about 5-7 minutes. If a thicker filling is desired, whisk in cornstarch that has been dissolved in a little water and cook for another 2-3 minutes.
9. Cool Filling: Remove from heat and let the filling cool completely before using.
10. Frosting (optional): Beat the heavy whipping cream with powdered sugar and vanilla extract until soft peaks form.
11. Assemble the Cake: Place one cake layer on a serving platter. Spread half of the strawberry filling on top. Add the second cake layer on top and spread with the remaining filling. Frost the top with whipped cream if desired.