• Melt vegan butter and coconut oil in a small saucepan over low heat. Once melted, remove from heat and stir in vanilla extract.
• Preheat oven to 375°F. Butter a 9-inch by 13-inch baking dish and line it with parchment paper, and butter it also.

For the crumb layer:

• In a mixing bowl whisk together whole wheat pastry flour, baking soda, sea salt, and ground ginger. Add rolled oats, light brown sugar, and coconut sugar. Whisk to blend; break up small clumps of brown sugar with your fingertips.
• Pour melted butter mixture over rolled oat mixture. Stir with a spatula until the mixture is evenly combined.
• Press ⅔ of the mixture into the prepared baking dish, and set aside the remaining third.

For the strawberry rhubarb layer

• Add diced strawberries and rhubarb to a medium mixing bowl for the filling. Add organic cane sugar, orange zest, and orange juice, stirring to combine. Stir in arrowroot powder.
• Pour strawberry and rhubarb mixture over the bottom crumb layer in baking dish. Evenly sprinkle remaining ⅓ crumb mixture over top.
• Bake in preheated oven until top is golden brown. Bake for 45 to 50 minutes until the top of the crisp is golden and the fruit filling is bubbling.
• Cool completely on a wire rack for 3 hours, then lift the bars out of the pan with the parchment paper before cutting into squares. Serve with vegan vanilla ice cream if desired.