Preheat your oven to 375°F and line a cookie sheet with parchment paper.
In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, and salt. Cut in the cold butter until the mixture resembles coarse crumbs.
Pour the heavy cream into a measuring cup, then stir in the vanilla extract. Gradually mix into the dry ingredients until just combined, being careful not to overwork the dough.
Transfer the dough to a floured surface. Scatter the berries on top and gently fold them into the dough.
Divide the dough in half. Shape each half into an 8-inch round disc, then cut each disc into 8 wedges. Place the wedges on the prepared cookie sheet, spaced about 2 inches apart.
Bake in the preheated oven for 18-20 minutes, or until the scones are golden brown and baked through.
To make the glaze, in a medium bowl, combine the powdered sugar, lemon juice, water, and vanilla extract. Whisk until smooth and well combined. If the glaze is too thick, you can add a little more water, a few drops at a time.
Once the scones have cooled after baking, drizzle the glaze over the top of each scone. If desired, sprinkle poppy seeds over the glazed scones for added texture and flavor.