1) Cut out a circle from a sheet of greaseproof paper (a cartouche) to have the same diameter as a medium saucepan. Put the butter, carrots, turnips, water, and salt in the saucepan and set over medium heat.
2) When the butter has melted, cover the saucepan with the paper. Cook the vegetables until tender and then smash to a puree.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.