In response to the first question: I am not a fan of adding vinegar/lemon juice to regular milk and calling it buttermilk. It is not the same. You will absolutely notice a difference. You'd be better off using plain yogurt, possibly thinned with a bit of milk, because you'll get a better consistency and a more near flavor to real buttermilk.
But really, you should just use real buttermilk. One, it's cheap. Two, in my experience, it lasts forever. In the three or four years since I started keeping it around as a staple, I have never once had a bottle of it go bad. Even after two or more months. Three, it is just not an ingredient that really substitutes well. You'll get the best flavor, texture, and height when you actually use buttermilk instead of a substitute. I obviously feel way too strongly about this.
So now you've bought yourself a quart of buttermilk. And here's answer to question number 2 - How do I use this stuff up?
- Homemade Ranch Dressing - So amazing, I want to weep when I don't have any around.
- Maple Oat Scones - The first scones I ever made. Delicious and got me over my fears of scone-making.
- Waffles - I've mentioned these waffles before but they are my favorite favorite waffles of all-time. I go 100% white wheat flour and use coconut oil and they are delicious. But I used vegetable oil for years and they were great that way too.
- Coconut Buttermilk Syrup - I love this recipe, and Bart and I both scarf it down whenever I make it. I halve the amount of butter, though, because I find it to be WAY too greasy with the full amount. And usually I halve the recipe because it make a lot and there are only three of us.
- Oatmeal Pancakes - These are some of my very favorite pancakes. Any weekend I remember to put them in the night before is a good one. A little jam and yogurt on top, and life is lovely.
- Buttermilk Biscuits - I love these slightly-sweet, flaky biscuits. Easy and delicious every time.
- Pumpkin Scones - For when you want to use up your buttermilk in a festively seasonal way.
- Perfect Potato Salad - I love the idea of potato salad, but find that most recipes fall a little flat. This one, though? I'm scraping the bowl.
- Cinnamon Doughnut Muffins - My clearest memory of these muffins is making them to eat at the top of Y Mountain with my roommates for a late-night birthday hike. They were good then and they're good now.
- Buttermilk Banana Bread - Bart doesn't really like this recipe (although he'll still eat several slices), but I LOVE this stuff and the first time I made it for Ella, she ate half a mini-loaf on her own.