Icecream Sandwich

Preheat oven to 180 deg c for 10 min. Butter a 15-by-10-inch pan; line with parchment paper, leaving a 2-inch overhang on the two shorter sides.

In a medium bowl, whisk together butter and sugar until combined; whisk in egg, vanilla, and salt until combined.

Using paper overhang, lift cake onto a work surface. With a serrated knife, halve crosswise. Place one half of cake, flat side down, on a large piece of plastic wrap. Spread with ice cream, then top with remaining half of cake, flat side up.

Return ice-cream sandwich to baking pan, and wrap tightly in plastic. Freeze until firm, about 2 hours.

Unwrap sandwich; using a serrated knife, cut into 8 rectangles, wiping off blade between each cut. Serve ice-cream sandwiches immediately.