Berry Lemon Curd Trifle

In heatproof bowl or top of double boiler over gently simmering water, whisk together eggs, egg yolks, sugar, and lemon rind and juice; cook, whisking frequently, until mixture is translucent and mounds on spoon, about 6 minutes. Remove from heat. Add butter; stir until melted. Pour lemon curd into large bowl or airtight container; place plastic wrap directly on surface and refrigerate until chilled, about 1 hour. (Make-ahead: Refrigerate for up to 24 hours.)

Meanwhile, cut cake into 1/2-inch (1 cm) cubes; place in separate bowl. Sprinkle with raspberry cocktail concentrate and let stand until absorbed, about 5 minutes.

In large bowl, whip cream; fold 1-1/2 cups (375 mL) into lemon curd; reserve remaining whipped cream.

Spread one-third of the lemon curd mixture in 10-cup (2.5 L) glass bowl. Top with half of the cake; sprinkle with one-quarter each of the raspberries and blueberries. Repeat layers once. Top with remaining lemon curd mixture; spoon reserved whipped cream over top. Top with remaining raspberries and blueberries. (Make-ahead: Cover with plastic wrap and refrigerate for up to 2 days.) Garnish with mint sprigs.