Step 1: Prepare the Brownie Layer

Preheat the Oven: Set your oven to 350°F (175°C). Grease and line a 9x13-inch baking pan with parchment paper.

Mix the Wet Ingredients: In a large bowl, melt the butter and mix in the granulated sugar and brown sugar until smooth. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.

Combine Dry Ingredients: In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt. Gradually fold this into the wet mixture until just combined.

Bake: Pour the batter into the prepared pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Allow the brownies to cool completely before cutting them into bite-sized squares.

Step 2: Make the Raspberry Sauce

Cook the Raspberries: In a medium saucepan, combine the raspberries, sugar, and lemon juice. Cook over medium heat, stirring occasionally, until the raspberries break down and the sauce thickens, about 10 minutes.

Strain (Optional): If you prefer a seedless sauce, strain the mixture through a fine-mesh sieve to remove the seeds. Let the sauce cool completely.

Step 3: Whip the Cream

Chill the Equipment: Place your mixing bowl and beaters in the freezer for about 10-15 minutes.

Whip the Cream: Pour the heavy cream into the chilled bowl and begin beating on medium speed. Once the cream starts to thicken, add the powdered sugar and vanilla extract. Continue beating until stiff peaks form. Be careful not to overbeat.

Step 4: Assemble the Trifle

Layer the Ingredients: In a large trifle bowl or individual serving glasses, start with a layer of brownie squares. Next, spoon a layer of raspberry sauce over the brownies, followed by a layer of whipped cream. Repeat these layers until you reach the top of the bowl, ending with a layer of whipped cream.

Garnish: Top the trifle with fresh raspberries, chocolate shavings, and a sprig of mint if desired.

Step 5: Chill and Serve

Chill: Cover the trifle with plastic wrap and refrigerate for at least 2 hours to allow the flavors to meld.

Serve: Once chilled, serve the trifle cold, ensuring each serving includes all layers.