Cut out a parchment paper circle (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. When the butter has melted, cover the saucepan with the parchment paper cartouche. 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.