Yes, to require your customers to buy a specific product in the Mix & Match bundle, simply create a Mix & Match bundle in Bundler > click “Create bundle” button > select the “Mix & Match bundle” option. 

Then, after you add available products to the bundle, simply turn on the “Required” checkbox next to the products you want your customers to buy to get a discount. 

This will then mean that the customers will have to have these required products in the cart AND fulfill your other Mix & Match bundle requirements (should you set them up) to get a bundle discount.