Heat the milk just until hot but not boiling, remove from the heat, add the tea bags, cover, and steep for 15 minutes. Press the tea bags well to extract flavor, then discard them, and cool the infused milk until just lukewarm or room temperature before mixing it into the batter. You should still have close to 180 ml — top up with a little extra milk if it's slightly short.

Heat the oven to 175°C conventional / 160°C fan. Grease a 9x5-inch loaf pan and line it with parchment, leaving overhang on the long sides for easy lifting.

Whisk together the flour, baking powder, salt, and finely ground Earl Grey tea leaves in a medium bowl until evenly combined, breaking up any tea clumps well so the flecks distribute evenly through the loaf.

Beat the softened butter and sugar together in a large bowl for 3 to 4 minutes until light, creamy, and slightly fluffy. Proper creaming at this stage is what gives the loaf its fine, tender crumb once baked.

Add the eggs one at a time, beating well after each addition and scraping down the bowl as needed. Beat in the orange zest and vanilla — if the mixture looks slightly curdled at this stage, that's normal and nothing to worry about.

Mix the sour cream and orange juice into the cooled Earl Grey milk. Add the dry ingredients to the butter mixture in 3 additions, alternating with the Earl Grey milk mixture in 2 additions, beginning and ending with the dry ingredients, mixing on low speed or folding gently just until combined after each addition. Don't overmix once the flour goes in — the finished batter should be thick, smooth, and evenly flecked with tea.

Scrape the batter into the prepared pan and level the top, then bake for 55 to 65 minutes, until the loaf is well risen, deeply golden on top, and a skewer inserted in the center comes out clean or with a few moist crumbs. The internal temperature should read about 95–98°C in the center. Tent loosely with foil during the last 15 to 20 minutes if the top is browning too quickly before the center bakes through.

Let the loaf cool in the pan for 15 minutes, then lift it out using the parchment and transfer it to a wire rack. Cool completely before glazing — a loaf that's even slightly warm will melt the glaze and let it soak in too much rather than sitting cleanly on top.

Whisk together the powdered sugar, orange juice, orange zest, and salt until smooth, adjusting with a few extra drops of orange juice if needed. The glaze should end up thick but pourable, so it drizzles and sets rather than disappearing into the loaf.

Drizzle the glaze over the cooled loaf and scatter a little extra orange zest over the top while the glaze is still wet. Let the glaze set before slicing into 10 pieces.