Arrange oven racks so top rack is closer to broiler and second rack is in center of oven. Place a large sheet of foil on top rack. (Foil should cover rack.) Preheat oven to 400°. Line 2 baking sheets with parchment paper.

Place diced pears on one prepared baking sheet.

Roast pears for 20 minutes on lower rack. Let cool completely on a wire rack.

Increase oven temperature to 425°.

In the work bowl of a food processor, pulse together flour, granulated sugar, baking powder, salt, and cardamom until combined. Add cold butter, and pulse until mixture resembles coarse crumbs. Transfer mixture to a large bowl. Add roasted pears and 1 cup half-and-half, folding in until mixture is combined and evenly moist. (If dough seems dry, add more half-and-half, 1 tablespoon at a time.)

Turn out dough onto a lightly floured surface, and gently knead 4 to 5 times. Using a rolling pin, roll out dough to a 1-inch thickness. Using a 2-inch fluted square cutter, cut 12 scones from dough, rerolling scraps once. Place scones ½ inch apart on remaining prepared baking sheet.

In a small bowl, whisk egg. Brush tops of scones with egg.

In a medium bowl, stir together sliced almonds, brown sugar, and honey. Spoon almond mixture on top of scones, dividing evenly.

Place baking sheet on lower rack, ensuring foil on top rack completely covers scones. (This will prevent excess browning of almond topping.)

Bake until edges of scones are golden brown and a wooden pick inserted in centers comes out clean, 8 to 10 minutes.