Preheat oven to 350 degrees F. Have ready 3 greased and floured 9 inch round cake pans.
Prepare the chocolate cake first. In a mixing bowl, stir together flour through cocoa powder. Add the oil, milk, egg, vanilla and stir until well mixed. Stir in the boiling water or coffee. Beat with an electric mixer for about 30 to 60 seconds or until smooth, then pour into the pan. Bake for about 30 minutes. Let cool in pan for 10 minutes, then invert onto a rack and let cool completely.
While chocolate cake bakes, wash out the mixing bowl and beaters and start preparing the other two batters. Try to time it so they’re ready to go in the oven a little after the chocolate cake is ready. You don't want to let the batters sit too long.
For each of the two batters, measure out the flour, baking powder and salt in separate bowls. Set aside
Working with two mixing bowls, put the butter and sugar for each batter in a mixing bowl. With an electric mixer, cream the butter and sugar in each bowl. Add one egg to each bowl and beat until light and fluffy, then add the flavorings. To one bowl, beat in the vanilla. To the other, beat in the strawberry Jell-O, and both extracts.
With a big spoon or a heavy duty scraper, add the flour and milk alternately, beginning and ending with the flour, to the yellow batter and mix by hand until smooth. Batter will be thick. Repeat procedure with the strawberry batter.
Put the batter into two cake pans and bake at 350 for 30-35 minutes or until a toothpick inserted comes out with moist crumbs. Let cool in the pans for 10 minutes, then invert and let cool completely.
To assemble, frost and stack the cakes so that the chocolate is on the bottom, vanilla is in the center and strawberry is on top. Or stack it the way you want. It's not like I'm the queen of everything and you have to follow orders.
Frosting: Beat 3 sticks (12 oz) softened unsalted butter until smooth and creamy. Gradually add 4 ½ cups of powdered sugar. After adding about half of the sugar, add 3 tablespoons of heavy cream and continue beating in remaining sugar. Continue beating and scraping sides of bowl, adding whole milk as needed, until you reach a smooth consistency. For a sweeter frosting, add a little more powdered sugar and milk. Beat in a pinch of salt (or omit if you used salted butter for some reason).