Preheat oven to 350°F (177°C).
Line a baking sheet with parchment paper. Spread oats in an even layer onto the prepared baking sheet. Place into the preheated oven and bake for 5 minutes.
Remove from oven and shake and flip the oats in the pan. Evenly spread the sliced almonds over the oats. Place back into the oven and bake for 5 to 8 minutes, or until almonds are lightly toasted and oats have a nutty aroma. Remove and transfer to a large bowl to cool slightly.
Increase oven temperature to 375°F (190°C).
Sprinkle the Redpath® Golden Yellow Sugar, all-purpose flour, the Redpath® Granulated Sugar, and salt into the oat-almond mixture. Toss to coat the oats and almonds. Drizzle in the melted butter and vanilla extract; stir to combine, ensuring everything is evenly coated with the butter. Cover and set aside.
Grease the bottom and sides of a 9-inch square baking pan with butter or baking spray.
In a small bowl, rub together the Redpath® Granulated Sugar with the lemon zest until oils and fragrance are released. Sugar will resemble wet sand. Stir in the finely chopped basil leaves until evenly distributed.
In another small bowl, whisk together the flour, salt, and cinnamon.
In a large bowl combine blueberries, and lemon juice. Toss to coat berries.
Sprinkle the sugar mixture and flour mixture over the blueberries. Stir to evenly coat blueberries with the mixture until no dry ingredients remain at the bottom of the bowl.
Transfer blueberries into the prepared pan. Sprinkle the oat-almond topping over the berries in an even layer. There should be varying clumps of the crisp topping. If not, squeeze pieces of the topping together to create larger pieces; this ensures a more textured and crunchier topping. Do not pat down the topping as this prevents steam from escaping.
Place into the preheated oven and bake until top is a deep golden brown and filling is vigorously bubbling around the edges of the pan and/or through any cracks in the topping; 35 to 40 minutes (see Chef’s Tips). Remove from the oven and place onto a wire cooling rack to cool slightly; 10 minutes.
Serve warm as is or with vanilla ice cream. Garnish with fresh basil leaves and/or lemon zest, if desired. Any leftovers can be stored in an airtight container at room temperature for up to 3 days or up to a week in the refrigerator.
*Topping can be made the night before or a few days in advance and stored in the fridge. Alternatively, it can be made, placed in a flat layer in a freezer-safe bag, frozen, and used at a future date. A few additional minutes may be needed for the topping if using straight from frozen.
*Chopped almonds, hazelnuts, or pecans can be substituted for the sliced almonds.
*Large flaked oats are also known as old-fashioned oats or rolled oats. Quick oats can be used in place of the large flaked oats, but note that the texture will be less crisp as the oats are thinner and cut into pieces. Instant oats are not recommended, as these oats are thinner than quick oats and break more readily into smaller pieces. They will likely produce a topping that is soft instead of crunchy.
*Redpath® Dark Brown Sugar can be substituted for the Redpath® Golden Yellow Sugar, creating a topping that has a more pronounced caramel flavor.
*The basil can be omitted entirely if a more classic blueberry crisp is desired or if basil is unavailable.
*Frozen blueberries can be substituted for fresh blueberries if not available or not in season; do not thaw. Additional time may be required when baking to ensure the blueberry filling is cooked through.
*Other seasonal berries can be substituted for the blueberries (e.g. blackberries, cherries, strawberries), or a mix of berries can be used.
*Any 2-quart (8-cup) baking dish can be used for the baking pan. If using a glass baking dish, lower temperature by 25°F (14°C) and bake longer; approximately 10 minutes.
*If the crisp is browning too quickly before the filling is done, cover the pan with aluminum foil to prevent burning.
*To ensure that the filling and flour have fully cooked through, especially if using frozen blueberries, check to ensure the internal temperature of the crisp has reached 175°F (79°C) with a thermometer.
*Completely cooled crisps can be wrapped well in plastic wrap or aluminum foil, placed into a freezer-safe container or bag, and frozen for up to 3 months. Alternatively, you can freeze the blueberry crisp unbaked and wrap well, and bake from frozen (best using a metal baking pan, if doing so, so that it can go from the freezer straight into the hot oven) for up to 3 months. Add 15 minutes baking time to ensure blueberries and topping are fully baked through and crisped.
*Serve crisps warm or at room temperature with vanilla ice cream, lightly sweetened whipped cream, or Greek yogurt.