Strawberry-rhubarb crisp

It's hard to cook this time of year. It begins in March, when the winter starts to be too long, and then 'spring' rolls around, and every year I somehow expect there to be fresh local produce in April. Who am I kidding? The motherload of fresh produce doesn't really exist in any form until July, and really only truly arrives in August and September. I grow weary of hearty greens and citrus, and crave berries and tomatoes. But what is it that I REALLY want? Strawberry-rhubarb crisp. Every spring I want this. This year, however, I actually get to make one. How, one might ask, do I have both such fruits in April? I have to thank both my husband and our gigantic freezer in the basement. Husband, because he bought armfuls of rhubarb last year, despite my protest that it was way too much. The freezer I thank for being so deep that I forget what's in the bottom, otherwise I surely would have eaten the rhubarb months ago. For an early taste of spring, I'll make this:

Strawberry-rhubarb crisp
Filling:
2lbs. rhubarb, cut into 1/2in. slices
1.5lbs. strawberries, halved
1C. sugar
3T. cornstarch
1T. lemon juice (~1/2 a lemon)
1/8t. salt
Topping:
2/3C. flour
3/4C. packed brown sugar
1/4t. salt
1/2C. rolled oats
1/4-1/2C. nuts (almonds, walnuts, pecans or a mixture)
1/4t. nutmeg

Preheat oven to 425 degrees F. Combine all ingredients for filling in a large bowl and mix carefully; spoon filling into a 3-quart baking dish. Stir together dry topping ingredients in a bowl, then blend in butter with a pastry cutter or fork until a coarse mixture is formed. Spoon topping evenly over filling. Bake until fruit is bubbling and topping is lightly browned, 45-60 minutes (slightly longer if using frozen fruit).