We bet we know the culprits: almost-empty jars of various pastes and sauces ... When you put your half-used jar of pesto back in the fridge, do what you can to preserve what’s left.

Start by pouring a splash of your favorite milk or coffee creamer into the jam jar—vanilla, caramel or even sweet cream will work beautifully. Secure the lid and give it a good shake to loosen up the ...