Into a large bowl, measure molasses, brown sugar, butter, baking soda, salt, spices, eggs, and 1 1/2 cups flour.
Beat ingredients at low speed just until mixed, then increase speed to medium and beat for 2 minutes.
With wooden spoon, or mixer, stir in about 3 cups flour to make a stiff dough. (I recommend a Kitchen-Aid mixer for this job.).
Wrap dough in plastic wrap and refrigerate until ready to use.
Roll dough to about a 1/4 inch thickness. (I do this between two sheets of plastic wrap to avoid a floury mess and to keep dough from getting tough.) Cut into desired shapes and place on a parchment lined baking sheet.
Bake at 350 degrees for 8-10 minutes. Baking time varies for me depending on how thick the cookie sheets are, how thick the dough is rolled out, and how big the shapes are, ie. gingerbread walls take a little longer.