In a large mixing bowl, whisk together the flour, ginger, cinnamon, cloves, nutmeg, and salt. Ensure there are no lumps in the spices so the flavor is evenly distributed throughout the dough.
In a separate large bowl or a stand mixer, beat the softened butter and brown sugar together until the mixture is light and fluffy. This should take about 2 to 3 minutes on medium speed.
Add the egg, molasses, and water to the butter mixture. Beat well until everything is fully incorporated. The mixture should look dark and glossy.
Gradually add the flour mixture to the wet ingredients. Mix on low speed until a stiff dough forms. If the dough is too crumbly, add a teaspoon of water at a time until it comes together. Divide the dough into two disks, wrap them in plastic wrap, and refrigerate for at least 2 hours or overnight.
Preheat your oven to 350°F (175°C). On a piece of parchment paper, roll out the dough to about 1/4-inch thickness. Place your house templates on the dough and cut out the walls and roof pieces using a sharp knife. Remove the excess dough scraps.
Slide the parchment paper onto a baking sheet. Bake for 12 to 15 minutes, or until the edges are firm and slightly browned. Let the pieces cool completely on the baking sheet to ensure they remain flat and sturdy.
While the gingerbread is cooling, make the icing by whisking the egg whites and cream of tartar until frothy. Gradually add the powdered sugar and beat on high speed for 7 to 10 minutes until stiff peaks form. This icing acts as the “glue” for your house.
Pipe royal icing along the edges of the wall pieces and join them together on a sturdy base. Hold them in place for a few minutes until the icing sets. Once the walls are dry, attach the roof pieces. Allow the house to dry for at least 2 hours before adding heavy candy decorations.