Preheat and prepare the pan: Preheat the oven to 350°F (175°C). Line a 9x13-inch pan with parchment paper leaving a 1–2" overhang on two sides for easy removal; lightly butter the exposed pan edges. This ensures the bars release cleanly and parchment protects the bottom from over-browning.

Make the streusel first so it can remain cold: In a medium bowl, combine 120 g (1 cup) of the all-purpose flour, 110 g packed brown sugar, and 48 g (half a box) instant lemon pudding powder. Add 113 g (1 stick) very cold unsalted butter cut into small cubes. Using a pastry cutter or two forks, cut the butter into the dry mixture until it resembles coarse crumbs with some pea-sized bits. Stir in 1/4 tsp almond extract if using. Keeping the butter cold gives you a streusel that will crisp in the oven rather than melt into the batter — you want distinct crunchy pieces on top.

Chill the streusel: Place the streusel bowl in the refrigerator while you make the batter. Cold streusel holds its shape and caramelizes into crunchy topping instead of integrating into the wet batter.

Whisk dry ingredients for the base: In a large bowl, whisk together 240 g (2 cups) all-purpose flour, the 96 g instant French vanilla pudding mix, 1 tsp baking powder, 1/2 tsp baking soda and 1/2 tsp salt. The pudding powder in the dry mix will add moisture, a custardy crumb and stability — it’s the secret to a tender, slightly dense bar that still slices cleanly.

Cream butter and sugar (warm butter method): In the bowl of a stand mixer fitted with the paddle (or using a large bowl and a hand mixer), add 113 g (1/2 cup) of the unsalted butter at room temperature and 150 g granulated sugar. Beat on medium speed until the mixture is pale and slightly aerated, about 2–3 minutes. The aeration helps the bars rise gently and gives a lighter crumb. Scrape down the bowl.

Add eggs and extracts: Add the 3 large eggs one at a time, beating briefly after each so the batter emulsifies — this builds structure and prevents butter from separating. Beat in 1 tsp vanilla extract and 2 tsp orange extract (and 1 drop orange food coloring if using) to distribute the orange flavor evenly through the batter.

Combine wet and dry: With the mixer on low, add half of the dry mixture, then 40 g (about 2 1/2 tbsp) whole milk, then the rest of the dry mixture. Mix just until incorporated — overmixing develops gluten and will toughen the bars. The pudding powder in the dry mix will hydrate with the egg and butter to give an almost custardy interior.

Fold and finish batter: Scrape the batter into the prepared pan and smooth into an even layer. If the batter feels too stiff to spread easily, wet your spatula slightly — you want a uniform surface so the streusel bakes evenly.

Top with chilled streusel: Remove the chilled streusel from the fridge and sprinkle it evenly over the batter, pressing very lightly so some crumbs nestle in but the topping remains loose in places. Light pressing helps some streusel adhere and prevents large dry pockets, while leaving other crumbs exposed for crispness.

Bake and watch for doneness: Bake in the preheated 350°F (175°C) oven for 30–35 minutes. Rotate the pan halfway through for even browning. The bars are done when the streusel is golden, the edges are set, and a toothpick inserted in the center comes out with a few moist crumbs (not wet batter). The pudding powder makes the center set a bit more slowly; checking at 30 minutes prevents overbaking which would dry the bars.

Cool completely: Remove from oven and cool on a wire rack until just warm, then use the parchment overhang to lift the slab from the pan and cool completely on the rack. Cooling completely is essential — warm bars will crumble when you try to slice them.

Make the orange glaze: In a small bowl whisk together 120 g (1 cup) powdered sugar with 1/2 tsp orange extract and 1–2 tbsp (15–30 g) whole milk until smooth and thick but drizzleable. If you’d like a brighter color, add a single drop of food coloring. Drizzle over the cooled bars using a spoon or a small piping bag. The glaze adds a sweet citrus sheen and helps set the top so slices look finished.

Slice and serve: After glazing, let the glaze set 10–15 minutes, then slice into 12 even bars (3 rows × 4 columns). For clean slices, warm a sharp knife under hot water, dry it, and slice in a single steady motion wiping the blade between cuts.