Line a 9 x 13-inch metal pan with parchment paper, allowing an overhang for easy removal later. Don’t skip this step, as it helps ensure your cake comes out perfectly!
Lightly coat the parchment with cooking spray. If you prefer not to use parchment, you can grease the pan directly with a spritz of cooking spray.
Preheat your oven to 350 degrees Fahrenheit. This ensures even baking and a nice rise on your cake.
In a large mixing bowl, whisk together the eggs using a fork. The eggs should be well beaten, creating a uniform mixture.
Add in the sour cream, melted coconut oil, and vanilla extract. Stir until completely combined; you want a smooth mixture to form.
Next, gradually add the cake mix and instant vanilla pudding mix, then fold in the coarsely chopped white chocolate chips. Mix well but avoid overmixing; it’s okay if the batter is slightly lumpy.
Pour in the buttermilk (or warm water) and mix until just combined. The batter should be thick and glossy.
Pour the batter into the prepared pan and spread it evenly. Bake according to the package directions for a 9 x 13-inch pan. A toothpick inserted in the center should come out clean or with moist crumbs.
Once done, allow the cake to cool in the pan completely, preferably overnight. This helps enhance the flavors and keeps it moist.
After cooling, cut the cake into 1-inch cubes, using a metal spatula to lift them gently from the pan.
While the cake cools, prepare the strawberries. Remove the tops and stems, then thinly slice them. Place in a large bowl and sprinkle with sugar. Stir gently to combine and let stand at room temperature for 30 minutes, tossing occasionally.
For the cream filling, in a stand mixer fitted with the whisk attachment, combine heavy cream, powdered sugar, and vanilla paste. Whisk on low to combine, then gradually increase to high speed until medium-to-stiff peaks form, about 2 to 4 minutes.
In a separate large bowl, mix together the sweetened condensed milk and 1% milk. With a hand mixer, blend in the instant vanilla pudding mix until combined.
Gently fold the whipped cream into the condensed milk and pudding mixture, being careful not to deflate the cream. You want a smooth, fluffy filling.
To assemble, place about one-third of the cake cubes in the bottom of a trifle dish. Layer with one-third of the cream mixture and then one-third of the strawberries. Repeat the layers two more times, finishing with strawberries on top.
Serve immediately, garnished with fresh mint if desired. Enjoy the layers of flavor and texture in every spoonful!
