Last week with the help of my mentor, I modified a butterscotch cookie recipe so that I could add butterscotch soda to it. I don't recall where I got the recipe online, however do recall the contents.
Original recipe:
2 1/2 cups flower
1 1/2 eggs
1/2 tsp salt
1 3/4 cups brown sugar
12 tbsp butter
1 tbsp vanilla extract
1/2 tsp baking soda
1/4 tsp baking powder
I needed to add 4 bottles of butterscotch soda to the mix. Because SCIENCE!!! So I started by looking at what was in the soda. Each bottle was 288ml, they had vanilla extract but didn't list how much. They also had 30g of sugar, after some calculation I determined that 30g of sugar was roughly 133ml. Which is an interesting side note while sipping your drink, almost half of that is sugar in solution. I also looked up the conversion for ml to cups, 250ml is 1 cup, at least for this (there are actually 3 different conversions based on which "cups" you are using.
So I poured all four bottles of soda into a mixing bowl and found that I ended up with 6 cups, (I cheated and didn't actually do the math but the bowl had markings on it indicating that there was 6 cups of liquid. This obviously was way to much liquid for the recipe, so I poured it all into a pot and started reducing it down. I was told by my mentor that I should not boil it as that would burn the sugar, so I kept it just on the edge of boiling. 4 hours later I managed to get it reduced down to 1 3/8 cups or 343ml, I took this into account and factored out sugar from it.
1 3/4 brown sugar = 437ml
We need to displace some of this for the reduced soda, so 437ml - 353ml = 84ml brown sugar
It was also suggested in order to move water around to cut the brown sugar with white sugar as that is drier sugar. So 42ml brown sugar and 42ml sugar.
After the math, I have the following recipe:
2 1/2 cups flower
1 1/2 eggs
1/2 tsp salt
42ml (1/4 cup roughly) brown sugar
42ml (1/4 cup roughly) white sugar
353ml (1 3/8 cup roughly) reduced butterscotch soda
12 tbsp butter
1/2 tsp baking soda
1/4 tsp baking powder
I mixed the eggs, butter, soda, and both sugars into a mixing bowl and mixed them throughly.
I also mixed the flower, salt, and the baking soda and powder in another bowl.
I then added the flower mixture to the liquid mixture and stirred them until smoothly mixed.
I cooked the cookies at 375F for 9-10 minutes. This seemed about right for my elevation. The cookies turned out a little bready, but mostly correct. I think I need to remove some of the egg next time, that should take away the breadiness.