1.Preheat oven to 350°F.
2. Place the berries into a large bowl and add the lemon juice, lemon zest, sugar and cornstarch. Mix all ingredients then pour into a 9” x 12” baking dish.
3. Prepare the topping: combine the flour, sugars, salt, oatmeal in the bowl of a food processor and pulse briefly to mix. Add the butter and pulse until the mixture resembles coarse meal and the butter is the size of small peas. If the mixture is not coming together, add cold water, 1 teaspoon at a time. This can also be done by hand using a pastry cutter or electric hand mixer. Sprinkle evenly on top of fruit, covering completely.
4. Place dish on a sheet tray to catch any juices that may spill over. Bake for 45 – 50 minutes until top is brown and fruit is bubbly.
5. In a freezing cold metal bowl, whip the cream and sugar until soft peaks form, but do not over-whip. Use immediately or refrigerate, rewhipping may be necessary. An electric mixer is fine too. Alternatively, you can serve with vanilla ice cream.