Preheat oven to 350°F (177°C)
In a medium bowl, whisk together flour, baking soda, baking powder, and salt
In a large bowl, beat room temperature butter and 2 cups sugar until light and fluffy (5-7 minutes)
Gradually add 4 egg whites, beating until fully incorporated

Mix in 3 tsp vanilla extract, then alternately add the flour mixture and 2 cups whole milk in three additions, beginning and ending with flour

Pour batter into a 9×13-inch parchment-lined baking pan and bake for 35-40 minutes
Cool cake completely, then chill for 30 minutes before cubing
Purée 1 lb strawberries in a blender until smooth

Transfer to a heavy-bottomed saucepan and stir in 1/2 cup sugar. Cook over medium heat for 8-10 minutes, reducing to a syrupy saut
Reserve 1.5 lbs hulled and chopped strawberries for layering
In a chilled bowl, whip heavy cream with powdered sugar and 1 tbsp vanilla extract until stiff peaks form

Layer cake cubes in a trifle dish, brush with cooked strawberry syrup, top with chopped strawberries, then apply a thick layer of whipped cream. Repeat two more layers, finishing with an uncovered whipped cream layer
Chill trifle for at least 1 hour before serving. Garnish with fresh strawberries and additional whipped cream if desired