Author Notes: I started making this filling to sandwich between macarons (page 288), and I ended up using it to sandwich cookies and whoopie pies (page 200) and to tuck inside mini cakes, muffins, cupcakes and even chaussons (page 256). It spreads and pipes beautifully, sets firmly and melts just as it should—right on your tongue.
In France, part of the butter in the recipe would be a salted butter that is distinctly (rather than mildly) salted. Because the amount of salt in American butters is usually low by comparison and because the level varies, I use unsalted butter and then add as much salt as I want. I like fleur de sel in the caramel, but you’ll find the salt you like and the amount you prefer.
Makes: about 1 cup
cups (140 milliliters) heavy cream
cup minus 2 tablespoons (175 grams) sugar
tablespoons (1 1/4 sticks; 5 ounces; 142 grams) unsalted butter, at room temperature and cut into 10 pieces
teaspoon fleur de sel or 1/4 teaspoon fine sea salt, or more to taste
- Bring the cream to a boil in a small saucepan on the stovetop or in a microwave oven. Remove from the heat.
- Pour the sugar evenly over the bottom of a wide high-sided skillet -- nonstick is great here. Put the skillet over medium-high heat and stay close, with a heatproof or wooden spatula in hand. When you see the sugar melting around the edges of the pan, start stirring, making small circular motions all around the edges and then, as more sugar melts, widening the circle. Cook and stir until the sugar turns a light blonde color -- think ale. Turn off the heat, stand back and add 4 pats of the butter. Swirl the pan or stir as the mixture sputters and then, still standing back, add the cream a little at a time. Return the caramel to medium-high heat and cook and stir until smooth, 1 minute or so. Stir in the salt.
- Carefully pour the caramel into a heatproof container (I use a 1-quart Pyrex measuring cup) and cool for about 20 minutes, stirring frequently. Ideally, you want the caramel’s temperature to go down to 140° F before proceeding.
- When the caramel has cooled, put the remainder of the butter in a small bowl and, using a flexible spatula, mix it until it has the consistency of mayonnaise. You can incorporate the butter with an immersion blender (my choice -- it’s why I pour the caramel into the measuring cup), blender, mini processor or spatula. Bit by bit, blend, process or beat in the butter, beating for at least 1 minute after each bit goes in and for another minute after all of the butter is incorporated. If you used a blender or processor, stir the caramel a couple of times to deflate some of the bubbles. Scrape the mixture into a container, press a piece of plastic film against the surface and refrigerate until chilled.
- Give the cold filling a couple of turns with a spatula before piping or spreading it.
- Storing: Covered tightly, the filling will keep in the refrigerator for up to 1 week.