1. Is there any reason that the butter, oil and water have to be heated in the oven instead of on top of the stove, or even in a microwave oven?
2. Does the pastry have to rest or cool in the refrigerator before baking?
1) You can also brown the butter mixture on the stovetop, but I can't vouch for the microwave -- you definitely wouldn't have as much control over developing the caramelized butter flavor, since it happens more quickly.
2) Nope! No resting or cooling needed whatsoever. Just dock it by pricking the bottom with a fork so it doesn't puff up in the oven.
Thanks, I try this the next time I make a tart.