Heat your oven to 375°F (190°C). Line a baking sheet with parchment paper.

In a large bowl, combine the flour, 3 tablespoons of the sugar, baking powder, and salt. Pinch the butter into the dry mixture with your fingers or cut it in until it resembles coarse cornmeal. Make a well in the center and pour in the half-and-half, then the egg. Use a fork to gently combine the egg and cream in the center, then use it to combine everything into a rough mass. Knead the mixture a few times into an even mass.

On a lightly floured counter, roll the dough to roughly a 10-by-6-inch rectangle. Sprinkle 1 tablespoon of the remaining sugar and 1 teaspoon of the cinnamon over half of the rectangle, then fold it in half. Roll the dough out again into an 8-by-6-inch rectangle; sprinkle another of the remaining tablespoons of sugar and the last teaspoon of cinnamon over half, then fold in half again. Pat the dough into roughly a 6-inch circle and cut with a sharp knife into 6 wedges. Space the wedges on the pan, sprinkle with the final tablespoon of sugar, and bake until slightly golden at the edges, 15 to 17 minutes.

Do ahead: Scones are better the first day. You can rewarm them in the oven briefly on the second day, but it might be a bit dry. You could make them and freeze them until needed instead. If baking from frozen, add 4 to 5 extra minutes in the oven.