1 cup water plus additional for blanching
1 1/2 cups granulated sugar, divided
1 (14-ounce) can sweetened condensed milk
3/4 cup chilled heavy cream
1 tablespoon confectioners sugar
1/2 teaspoon pure vanilla extract
1 (8- by 4-inch) store-bought all-butter pound cake (3/4 to 1 pound), chilled
Remove zest (peel) from 2 lemons in wide strips with a vegetable peeler (see Tips, page 118), then cut lengthwise with a sharp knife into 1/8-inch-wide julienne strips. Reserve lemons for juicing. Fill a 2-quart heavy saucepan halfway with water, then add julienned peel. Bring to a boil and simmer 15 minutes. Drain peel in a sieve and rinse. Bring water (1 cup) and 1 cup granulated sugar to a boil in saucepan, stirring until sugar has dissolved. Add peel and gently simmer until translucent, about 15 minutes. Remove peel from syrup with a slotted spoon, letting syrup drain off into saucepan. Spread out on a sheet of wax paper and cool to room temperature. Toss peel with remaining 1/2 cup granulated sugar, stirring with a fork to coat and separate. Transfer sugared peel to clean dry sieve and shake off excess sugar, then spread out on a fresh sheet of wax paper to dry slightly. Make lemon filling while peel simmers and cools: Grate enough zest from remaining 2 lemons with a rasp to measure 2 teaspoon, then squeeze enough juice from all lemons to measure 2/3 cup. Whisk together zest, juice, and condensed milk. Chill until cold, at least 30 minutes. Beat heavy cream with confectioners sugar and vanilla in a chilled bowl with a whisk or electric mixer until it just holds stiff peaks. assemble cake: Halve cake crosswise, then trim crust from all sides. Cut each block horizontally into 4 (1/2-inch-thick) squares. Halve each square diagonally into 2 triangles. For each serving, layer 2 triangles with lemon filling, offsetting corners. Top cake with whipped cream and candied lemon peel.