Things I'd like to spend a month working on

Ice cream and sorbet making

Cheese/dairy making, including creme fraiche, cream cheese, yogurt, butter

Sausage making

Pressure canning soups, stews, vegetables

Gluten free baked goods, especially bread

Pickled vegetables, including sauerkraut

Smoked meats +\or Home-cured bacon

Edit: Add, after thinking: Understand how to condition dried fruit such that it can be stored at room temperature safely.

Pastry making