**Yes—40% quark should work in this recipe, though you should expect a lighter, less rich cheesecake with a somewhat different texture.** The six eggs and ⅓ cup flour give it a good chance of setting successfully. [This discussion of the same recipe](https://cooking.stackexchange.com/questions/114355/can-i-substitute-quark-40-for-cream-cheese-in-basque-burnt-cheesecake-recipe) supports the substitution.

- **Taste:** Expect a slightly tangier, less buttery filling. With the sugar, vanilla and browned top, I’d expect the difference to be noticeable but pleasant.
- **Texture:** Quark generally contains more moisture than US block cream cheese. The cake may be softer and a little more crumbly or grainy, with less of the smooth, rich mouthfeel of the original. The result will depend on your quark’s consistency. [Substitution discussion](https://cooking.stackexchange.com/questions/114355/can-i-substitute-quark-40-for-cream-cheese-in-basque-burnt-cheesecake-recipe).

One relevant label detail: **“40%” usually means fat in the dry matter.** The actual fat content is much lower; for example, MILRAM’s 40% quark contains 10 g fat per 100 g. Check your tub’s nutrition panel. [MILRAM product information](https://www.milram-food-service.de/produkte/speisequark/speisequark-40-fett-itr-5-kg).

For your cake, I’d drain the quark overnight **in the refrigerator**, using a cloth-lined sieve over a bowl, especially if it has visible whey. Then weigh out **2 lb / approximately 907 g of drained quark**; you’ll need extra quark to allow for the drained liquid. Keep the remaining ingredients as written for this first attempt.

Bake using the recipe’s visual cues, allowing for a different baking time, and let it cool fully before judging the texture.