Line two baking sheets with parchment or silpats. Set aside.

In a heavy-bottomed saucepan, bring the milk, butter, water and salt to a full rolling boil. Add the Dijon mustard and return to a boil, remove the pan from the heat and add the flour- all at once. Stir vigorously with a sturdy spoon until all is combined then return the pan to medium-low heat, stirring vigorously still, until the dough comes together- balling up slightly around the spoon, and a thin film forms on the bottom of the pan. Stir hard for 1 minute. The dough should seem cohesive, but still soft enough to break apart with the spoon. Remove the pan from the heat and let the dough sit for 10 minutes, undisturbed. After 10 minutes, you should be able to stick your finger -up to the first knuckle- into the dough and hold it there for several seconds before it becomes uncomfortable. In other words, it should be hot, but not blisteringly so.

Transfer the dough to the bowl of a stand mixer (or a large bowl in which you can use a hand mixer or a sturdy spoon and some serious effort). Add the eggs, one at a time, and beat well after each addition. After the last egg is added, beat the dough for 2 minutes before beating in the grated cheese and scallions.

You can use spoons, dishers or a pastry bag to portion out the pastry, but it must be done immediately! I prefer to use a disher (cookie scoop) or pastry bag to pipe out mounds that are about 1-1/2 tablespoons in size. Leave enough room between the mounds so that they are not touching. Immediately put the pan into the freezer and freeze until firm, about 6 hours. When they are hard to the touch, you will use a spatula or your hands to transfer all of the mounds to a re-sealable plastic freezer bag or container with a tight fitting lid. Keep frozen for up to 3 months, baking as many gougères as you need at a time.

Preheat oven to 425°F. Line a baking sheet with parchment or a silpat and arrange desired number of frozen gougères so that there is at least 2 inches of space around each one to allow for expansion in the oven. Bake for 12 minutes, lower the oven heat to 375°F, rotate the pan(s) and bake for another 12-15 minutes, or until the gougères are puffed, firm, and deep golden brown. Serve warm for most pronounced flavour, or at room temperature.

Preheat oven to 425°F. Line two baking sheets with parchment or silpats. Set aside.

In a heavy-bottomed saucepan, bring the milk, butter, water and salt to a full rolling boil. Add the Dijon mustard and return to a boil, remove the pan from the heat and add the flour- all at once. Stir vigorously with a sturdy spoon until all is combined then return the pan to medium-low heat, stirring vigorously still, until the dough comes together- balling up slightly around the spoon, and a thin film forms on the bottom of the pan. Stir hard for 1 minute. The dough should seem cohesive, but still soft enough to break apart with the spoon. Remove the pan from the heat and let the dough sit for 10 minutes, undisturbed. After 10 minutes, you should be able to stick your finger -up to the first knuckle- into the dough and hold it there for several seconds before it becomes uncomfortable. In other words, it should be hot, but not blisteringly so.

Transfer the dough to the bowl of a stand mixer (or a large bowl in which you can use a hand mixer or a sturdy spoon and some serious effort). Add the eggs, one at a time, and beat well after each addition. After the last egg is added, beat the dough for 2 minutes before beating in the grated cheese and scallions.

You can use spoons, dishers or a pastry bag to portion out the pastry, but it must be done immediately! I prefer to use a disher (cookie scoop) or pastry bag to pipe out mounds that are about 1-1/2 tablespoons in size. Leave 2 inches of space around each mound to allow them to expand in the oven.

Bake for 12 minutes, then lower the heat to 375°F, rotate the pans from top to bottom and front to back, and bake another 12 minutes, or until they are puffy, firm, and golden brown. Serve warm for most pronounced flavour, or at room temperature.