"Mürbe" is a German adjective which means brittle, crumbly, friable or short in English. A short dough in baking means "a cookie or pastry dough with a high proportion of butter or fat to flour, producing a cookie or pastry with a rich, tender, and crumbly texture." (thebakingpan.com)
In the US and other countries, a short dough is made by cutting in the butter to the dry ingredients, then adding wet ingredients just to mix (pie crust) or by creaming the sugar and butter first (cookies). A shortened cake or butter cake contains solid fats and can also be made by creaming the butter and sugar first.
"Mürbeteig" also describes many different dough types.
- A shortbread cookie dough in the classic ratios of 1 sugar: 2 butter: 3 flour by weight is mixed together all at once and contains no leavening. A good example of this is the recipe for Checkerboard cookies.
- A type of kneaded dough, most often without leavening. This video on how to make a sweet Mürbeteig from the popular magazine "Essen & Trinken" (transcript here) shows a short pastry being made to line a springform pan which will hold a baked filling (akin to a pie). As you can tell by the mixing method, this crust will not be as flaky or tender as a US pie crust. However, if not over mixed it can be cookie-like, and if it contains some liquids such as egg or milk, it can even be cake-like (see Linzertorte for an example).
Related to the video but not the same are the most common "Mürbeteig" directions:
Mix together the dry ingredients and place on a work surface. Make a well in the mound of dry ingredients and in that well place the eggs and liquids. Around the lip of the well, set the butter in small pieces. Working from outside to inside, quickly mix the dry into the wet ingredients and knead until a smooth ball can be formed. This is often refrigerated to make it less sticky.
When confronted by these words, I usually change the recipe as follows: Cut the butter into the dry ingredients, mix all wet ingredients until well blended, then pour wet into dry and mix or knead until dough forms a ball. I have even tried creaming the butter and sugar together first, then adding the eggs and then the flour. The dough tends not to be as tough for me then. I do this because the classic German method often turns hard, and my family scrapes out the filling and leaves the crust. This makes me sad and I feel like I wasted all those ingredients. The above-mentioned methods work better for me.
- Spritz dough - butter, sugar and flour (or starch) is mixed together but not creamed. Then the milk or other liquid is mixed in to form a not-too-stiff dough which is placed in a decorator bag or a Spritz container ( ) and formed into cookies right on the baking sheet.
- Quark-Ölteig - Quark and neutral oil, such as sunflower seed or canola, are used instead of butter and other liquids. The quark is mixed with sugar and oil and egg if using, then the flour is added and kneaded to incorporate. This dough is very popular for sheetcake or onion cakes because people find it less daunting than making a yeast dough for the crust. In the US, yogurt cheese (drained yogurt) could be used instead of the quark.
See Classic Shortbread - Mürbeteig Recipe and Directions
See also Classic Savory Cake or Pie Dough Recipe - Salziger Mürbeteig