Red Pepper Jelly Rugelach

0 In the bowl of a stand mixer, beat together butter, cream cheese, and salt until light and fluffy, about 2 minutes. 
1 With mixer running on low, slowly add in flour. Beat on low until soft clumps form, about 1 minute more. 
2 Turn dough out on a lightly floured surface and knead a few times just to bring the dough together. Divide dough in half. Press each half into a round disk and wrap it tightly in plastic. Refrigerate for at least 2 hours and up to 2 days. 
3 When you’re ready to form the rugelach, line a large sheet pan with parchment paper. Spray an oven-safe cooling rack with nonstick cooking spray and place it on top of the sheet pan. (Note: This set-up is important. The cooling rack will allow excess red pepper jelly to drip off and away from the rugelach. The parchment will make clean-up easy.)
4 Remove one dough disk from the fridge and roll out on a lightly floured surface into a 12-inch round circle. Use your hands to gently shape the edges so they are even and smooth. 
5 Spread half of the jelly over the dough, leaving a small amount of space open around the edges. Sprinkle with half the cheese. 
6 Use a sharp knife or pizza cutter to slice the dough round into 16 even wedges (the same way you would slice a pizza). Working with one wedge at a time, starting at the wide end, roll the rugelach up into a crescent (some of the jelly will slip out of the sides, but that's okay). 
7 Line the formed rugelach up on the prepared cooling rack / sheet pan, leaving about an inch of space between each.
8 Repeat the process with the remaining dough round. 
9 Transfer sheet pan with the rugelach to the refrigerator and chill for 30 minutes.
10 Preheat oven to 350°F / 177°C.
11 Whisk egg. Brush the tops of the rugelach with egg. 
12 Bake until golden brown, rotating the pans halfway through cooking, 30 to 35 minutes.
13 Allow to cool on the cooling rack / sheet pan until cool enough to remove and transfer to a serving plate. (If they stick, run a sharp knife between the rugelach and the cooling rack to release.)