Prepare meringue layers:
Preheat oven to 300 degrees F. Line 2 large cookie sheets with foil. Using 8-inch round plate or cake pan as a guide, with toothpick, outline 4 circles on foil (2 on each cookie sheet).
In large bowl, with mixer at high speed, beat egg whites and cream of tartar until soft peaks form. Sprinkle in sugar, 2 tablespoons at a time, beating until whites stand in stiff, glossy peaks when beaters are lifted.
Spoon one-fourth of meringue (about 1 1/2 cups) inside each circle on prepared cookie sheets. With narrow metal spatula, spread meringue evenly to fill circles.
Bake meringues 45 minutes. Turn off oven; leave meringues in oven 1 hour to dry. Transfer meringues on cookie sheets to wire racks; cool 10 minutes, then carefully peel foil from meringues and cool completely. Store in airtight container at room temperature up to 1 week.
While meringues bake, prepare Lemon and Raspberry Fillings: From lemons, grate 1 tablespoon peel and squeeze 1/2 cup juice. In 2-quart saucepan, with wire whisk, mix cornstarch with lemon peel and juice until blended. Add butter and granulated sugar. Heat to boiling over medium-high heat, stirring constantly; boil 1 minute.
In small bowl, with whisk, lightly beat egg yolks. Into egg yolks, gradually beat 1/4 cup hot lemon mixture; pour egg mixture back into lemon mixture in saucepan, beating rapidly to prevent curdling. Reduce heat to low; cook, stirring constantly, until mixture thickens (do not boil), about 5 minutes. Pour into medium bowl. Press plastic wrap directly onto surface of custard. Refrigerate until chilled, about 3 hours or up to 3 days.
When ready to assemble dacquoise, in medium bowl, with mixer at high speed, beat cream and confectioners' sugar until stiff peaks form. Fold 1 cup whipped cream into cold lemon filling. Reserve 10 raspberries in cup and 3/4 cup whipped cream in small bowl; cover and refrigerate to use for garnish later. Fold remaining raspberries into remaining cream in bowl.
Assemble dacquoise:
Place 1 meringue layer on cake plate or round platter. Spread with half of lemon filling. Top with another meringue layer and spread with raspberry filling. Top with another meringue layer and spread with remaining lemon filling. Top with remaining meringue layer. Loosely cover dacquoise with plastic wrap and refrigerate 5 hours or up to overnight to soften layers slightly.
To serve, with whisk, beat reserved whipped cream (cream may have separated slightly) to stiffen. Spoon cream onto center of dacquoise; sprinkle with reserved raspberries. Garnish with mint.
