Step 1

1 For the cake: Preheat the oven to 350 degrees

Step 2

2 Grease an 8-by-8-by-2-inch square pan with softened butter or cooking oil spray

Step 3

3 Line the bottom with parchment paper

Step 4

4 Combine the light brown and granulated sugars in the bowl of a stand mixer or in a mixing bowl

Step 5

5 Sift the flour, cocoa powder, baking powder, baking soda, salt and espresso powder onto a sheet of parchment paper, then use the paper to pour the dry ingredients into the bowl

Step 6

6 (Or sift them directly into the bowl

Step 7

7 ) Beat on medium speed, until thoroughly incorporated

Step 8

8 Reduce the speed to low; add the egg and egg yolk, beating to incorporate after each addition, and scraping with a flexible spatula, as needed

Step 9

9 Add the vanilla extract and the oil, beating to blend well

Step 10

10 Finally, add the boiling water and heavy cream; once they are incorporated, increase the speed to medium and beat for 30 seconds, until smooth

Step 11

11 The batter will be quite thin

Step 12

12 Transfer to the pan, being mindful to scrape out every last bit of batter, as you will be using the bowl again to make the frosting

Step 13

13 Bake (middle rack) for 25 to 30 minutes, rotating the pan from front to back after the first 15 minutes, and checking for doneness with a toothpick at the center after 20 minutes

Step 14

14 The cake is done when the tester comes out with a moist crumb or two and the cake is just beginning to come away from the sides of the pan

Step 15

15 Let the cake cool in its pan for 10 minutes, then run a paring knife around the edges to release it

Step 16

16 Invert onto a serving plate to cool completely

Step 17

17 To make the frosting, rinse the same mixing bowl and paddle attachment or beaters, then add the butter and cream cheese and beat on medium-high speed until smooth

Step 18

18 Add the vanilla extract and salt, then beat again on medium-high speed

Step 19

19 Reduce the speed to low

Step 20

20 Add the confectioners’ sugar 1 cup at a time, sifting it over if it is lumpy and beating until incorporated

Step 21

21 Stop to scrape the bowl with a flexible spatula, as needed

Step 22

22 Once all the sugar has been added, increase the speed to medium, and beat briefly until smooth

Step 23

23 Do not overmix or the frosting will lose structure

Step 24

24 Use a generous hand and an offset spatula to spread the top of the cooled cake with the frosting

Step 25

25 Decorate with sprinkles, if using

Step 26

26 If you do not frost generously, you may have leftover frosting (lucky you)

Step 27

27 Cut just before serving