1. Prepare two eight by four inch (20×10-centimeter) loaf pans. Cut two pieces of aluminum foil, one for the length and one for the width of the pan. Make each piece long enough to extend over the rim of the pan. Press the pieces of foil into the pan as neatly as possible, gently pressing into the corners. Fold the excess foil over the rim. Spray the bottom and sides of the pan with cooking spray. Set the pans aside.
2. For the praline layer, microwave the praline paste in 20-second increments until soft and easy to work with.
3. In a large mixing bowl, cream the margarine. Add the vanilla. Add four tablespoons sugar and beat on medium speed for three minutes. Add one egg yolk at a time, scraping the bowl between each addition. After adding the last yolk, beat four minutes until very creamy. Add in softened praline paste and beat just until blended. Transfer to a medium mixing bowl.
4. In a clean and dry mixing bowl, beat egg whites and salt. Slowly add in the remaining two tablespoons sugar. Beat to soft peaks (do not overbeat). Slowly fold the whites into the praline mixture.
5. Divide the praline mixture evenly between the two loaf pans. Freeze for at least one hour.
It is highly recommended to use high-quality praline paste, packaged in one pound containers. It is generally very fresh and easy to work with. If necessary, microwaving at 10–15 second increments will soften and make the paste more manageable. (A can cannot go in the microwave — transfer into a microwaveable dish first). The praline paste is sold in Tips and Toque in Lakewood and Peppermill in Brooklyn. You may also purchase the canned praline paste that is available in all grocery stores. However, it will be more difficult to work with and need extra time for softening.