Put the A. ingredients in a heatproof container, and beat with a whisk until light and fluffy (or sift the ingredients together). Add the milk little by little, taking care not to form lumps.
Tear the sliced cheese into small pieces and add to the mixture. Microwave uncovered for 1 minute 40 seconds at 700w. Mix well.
Add the egg white and mix well to incorporate. Microwave for another minute.
Mix well with a spatula, add the butter and mix until melted.
Wrap in plastic and form a 15 x 18cm rectangle. When it has cooled, freeze.
Story Behind this Recipe
I uploaded the cheese fold-in sheet that I included in a previously uploaded recipe for marbled bread for cheese lovers, as a separate recipe. This is an unsweetened cheese sheet for savory bread.
My microwave oven is 700W. Please adjust the microwave time on your oven's wattage. Please refer to the directions for detailed how-tos. Unlike other fold-in sheets, this one is a bit on the loose side (since cheese hardens when cold).