Step 1

Preheat the oven to 375 degrees F.

Step 2

Line two sheet pans with parchment paper.

Step 3

Sift the all-purpose flour, the cake flour, 1/4 cup of the sugar, the baking powder, the salt, and the cinnamon together into a large bowl.

Step 4

Cut the butter pieces into the flour mixture until crumbs of various sizes form, ranging from sandy to pea-sized. Some large pieces of butter are fine.

Step 5

Gently stir in the chocolate chips.

Step 6

Gradually add in 1 1/2 cups of the buttermilk, stirring gently until there are no patches of dry flour mixture remaining, being careful not to overmix. If the mixture looks too dry, add more of the extra buttermilk a little at a time. The dough should be moist and slightly sticky.

Step 7

Using a large ice cream scoop, drop balls of the dough onto the prepared sheet pans, leaving about 1-inch between each ball.

Step 8

Brush the dough with the beaten egg and sprinkle each with the extra sugar.

Step 9

Bake the biscuits, turning the pans halfway through cooking, until golden-brown, about 20-25 minutes.

Step 10

Allow the biscuits to cool for 10 minutes.

Step 11

Serve with the jam.