In a large saucepan whisk together the sugar, eggs, egg yolks, lemon zest and juice. Cook, stirring constantly, over medium-low heat until the mixture reaches 160°F on a candy thermometer, about 8 to 12 minutes. Remove from heat. If the mixture is lumpy, strain through a fine mesh sieve. Add the butter, one piece at a time, whisking constantly and heating, as needed, over low heat to melt the butter. Transfer to a medium bowl, cover with plastic wrap touching the surface of the curd. Refrigerate for 2 to 3 hours, until the curd has cooled and thickened. Whisk in the mascarpone.
Toast pound cake pieces under the broiler until golden brown. In an 8-oz. glass, layer about 1/4 cup pound cake, ¼ cup lemon curd, and 2 Tbs. blueberries. Repeat layers once. Top with edible flowers, if using. Repeat with the remaining ingredients in 5 more glasses.