Add the cream and earl grey tea to a small pot. Heat over high heat, stirring often, until gently boiling. Remove from heat, cover, and let steep 8-10 minutes, or until the cream is light brown in color.
Strain the cream into a container and discard the tea leaves. Cover and refrigerate until cold.
Whisk together the flour, sugar, salt, baking powder, and tea leaves in a large bowl until thoroughly combined. Use a box grater to grate in the frozen butter. Mix with your fingers until a coarse, crumbly mixture forms. Put in the fridge while you prepare the wet ingredients.
In a separate bowl, whisk together ½ cup of the infused cream, egg, and vanilla. If you don't have enough infused cream, top it up with regular cream. Add to the flour mixture, then mix until combined and moist-looking. Fold in the frozen blackberries.
Lightly flour a work surface and your hands, then turn the dough out. For 16 small scones: Cut the dough in half. Form into two equal balls, then press each into a ~5 inch disk. Use a sharp knife to cut each disk into 8 wedges (as if you were cutting a pizza). For 8 large scones: form into one ~8 inch disk and cut using the same method.
Add scones to a parchment-lined baking sheet, placing them 2-3 inches apart. Brush scones with cream. Refrigerate on the baking sheet for 15-20 minutes.
Preheat the oven to 400º F. Bake for 18-22 minutes until golden brown.
Let cool until warm to the touch. While the scones cool, prepare the glaze. Add the blackberries (¼ cup for me was 7 individual berries) to a nonstick pan over medium heat. Cook, stirring frequently, until the berries are soft and releasing juice.
Set a strainer over a small bowl and add the cooked berries to the strainer. Use a spoon to push the juice through into the bowl. Add the lemon juice and powdered sugar, then mix until combined and bright pink.
Once the scones have cooled, drizzle them lightly with the glaze. If you prefer extra sweet scones, double the glaze recipe and coat the top of each scone.
