In a glass jar, stir together tequila, mezcal, cointreau, and fresh lime juice. Refrigerate until you’re ready to serve. This mixture will keep for a few days. When ready to serve, If you want a salted rim, pour salt into a small, saucer-sized plate, rub a lime wedge around the entire or part of the rim, dip the rim of the glass into the salt, and add ice to each glass. Pour the mixed cocktail over ice and enjoy. Garnish with lime and/or jalapeno slices