Many of you have questioned me about how thick the dough should be rolled before you apply the cookie mold and press. The single most common error I see when teaching Springerle classes is that students roll their dough to 1/8 to 1/4 inch thick as if they were making sugar cookies. The dough for Springerle cookies must be rolled at least 3/8 inch thick and I often find that 1/2 is a good thickness for deeper molds and very deep molds may require the dough to be even thicker.
Above, I have shown the top surfaces of two cookies made with the same mold. Though they are different images from the mold (M7615 Cassie's Garden) shown at the right, the carving on all images has similar depth. Both cookies have a nicely defined print after baking. You will note that there is somewhat more distortion on the right hand side cookie: the sides are slightly puffed in places, the top is slightly more domed and the rectangular shape is not as even. More dough and more rising will mean more distortion, so too thick is also problematic.
Take a look at the red arrows, which shows the thickness of the pressed cookies before they were baked. The dough on the left was thinner, and the dough on the right was thicker.
Take a look at a side view of the two broken cookies. Both thicknesses are fully baked with a fully formed dense cake like texture. On the left thinner cookie, most of the leavening has occurred on the bottom half of the cookie. The thicker cookie is more domed on the top; because there is more dough it has risen more on both the top and the bottom of the cookie. For both of these cookies the thickness of the dough was plenty deep enough to get a full impression of the carving. In my mind, these are both good thicknesses. They have both risen so that they are not hard discs, they have nice clean impressions and they have a dry cake-like texture.
But, the thinner cookie will get drier and harder more quickly, while the thicker cookie will stay somewhat softer which makes perfectly good sense. Personally, I prefer the thicker cookie. I am willing to have a slightly less perfect end result on the image and have a softer cookie. This decision ends up being a personal preference, so you will have to decide how thick to roll the dough to meet your preference.So the thickness you roll Springerle dough will differ depending on:
must be thick enough to to get a full impression of the carving plus have a minimum depth of 1/4 inch after pressing
if you are very strong and apply heavy pressure with the mold, roll the dough more thickly
your personal preference about a harder or softer cookie
your personal preference about how "perfect" you want the cookie to look
Some practice and experience will help you determine the best thickness for you.